Fix awkward descriptions: details on the tags were under the account tag requirements.

Thus, I factored the text regarding the linking to documents that was in the
Expense account section into the section on describing the tags themselves,
and then merely linked back to that.

npo-ledger-cli-tutorial.md

@@ -174,17 +174,35 @@ sides.  But, the `IncomeType` tag, which has no meaning for `Accrued:`
 accounts, so it is applied only to the `Income:Main Org:Donations` part of
 the transaction.
 
-### Tags Used In This System
+Below you'll find detailed descriptions of all the possible tags that are
+used in this system.  The actual declarations and enforcement of rules of
+these tags can be found in the file `accounts/config/config-tags.ledger` in
+this project.
 
-A list of tags can be found in the file `accounts/config/config-tags.ledger`
-in this project.
+
+### Documentation Tags
+
+Documentation tags are tags that link to other backup documents that provide
+evidence and details that justify a particular ledger entry.  The value of
+the tag is a relative path name of a file elsewhere in the same repository
+that documents the specific expense.  For example, an entry like this:
+
+     2012-02-05 Office Supply Galore - Online Order
+         Expense:Main Org:Office Supplies      $35.00
+             ;Receipt: accounts/documentation/org/receipts/2012-02-05_office-supply-galore.txt
+         Liabilities:Credit Card:Visa         -$35.00
+
+shows that a purchase was made at Office Supply Galore's online store for
+$35.00, and the file
+`accounts/documentation/org/receipts/2012-02-05_office-supply-galore.txt`
+contains the receipt from that purchase.
 
 #### Receipt Tag
 
 The `Receipt:` tag refers to receipt of some sort.  Typically, this is a
 document that shows clear confirmation that the transaction has already
 occurred.  The value of the `Receipt:` tag is always a valid pathname in the
-repository to the document.
+repository to the document, [as described above](#documentation-tags).
 
 Some examples of appropriate uses of the `Receipt:` are:
 
@@ -207,7 +225,7 @@ The `Invoice:` tag refers to an actual invoice, either generated by the
 organization or received by the organization.  Typically, this is a document
 that is a request for payment, rather than documenting an actual payment that
 has occurred.  The value of the `Invoice:` tag is always a valid pathname in
-the repository to the document.
+repository to the document, [as described above](#documentation-tags).
 
 Some examples of appropriate uses of the `Invoice:` tag are:
 
@@ -225,7 +243,9 @@ Some examples of appropriate uses of the `Invoice:` tag are:
 The `Statement:` tag refers to any sort of written statement received from an
 external party (or even perhaps generated internally) that provides document,
 insight, or other information about the transaction.  The value of the
-`Statement:` tag is always a valid pathname in the repository to the document.
+`Statement:` tag is always a valid pathname in the repository to the
+document, [as described above](#documentation-tags).
+
 
 Some examples of appropriate uses of the `Statement:` tag are:
 
@@ -241,6 +261,11 @@ Some examples of appropriate uses of the `Statement:` tag are:
   [receipt](#receipt-tag), but definitely is valid backup documentation for
   the transaction.
 
+### Information Tags
+
+In contrast to documentation tags, information tags can more traditionally be
+considered pure "meta-data" for a ledger entry.
+
 #### IncomeType Tag
 
 The `IncomeType:` tag is used for all `Income:` accounts.  This refers to the
@@ -275,22 +300,14 @@ account (primarily for use with Ledger CLI's `--pivot` and `--group-by`,
 
 ### Expense Account Documentation
 
-Each Expense account entries need to be tagged with an
-[`Invoice`](#invoice-tag), [`Receipt`](#receipt-tag), or
-[`Statement`](#statement-tag) tag.  The value of the tag is a relative path
-name of a file elsewhere in the same repository that documents the specific
-expense.  For example, an entry like this:
+Each `Expense:` account entry must be tagged with the following tags:
 
-     2012-02-05 Office Supply Galore - Online Order
-         Expense:Main Org:Office Supplies      $35.00
-             ;Receipt: accounts/documentation/org/receipts/2012-02-05_office-supply-galore.txt
-         Liabilities:Credit Card:Visa         -$35.00
+* One of: [`Invoice:`](#invoice-tag) [`Receipt:`](#receipt-tag), or
+  [`Statement`](#statement-tag).  (The only exception to this rule: an entry
+  does not need an `Invoice:`, `Receipt`, nor a `Statement` tag if the
+  [payee was never charged](#never-charged-payee).
 
-shows that a purchase was made at Office Supply Galore's online store for
-$35.00, and the file `accounts/documentation/org/receipts/2012-02-05_office-supply-galore.txt`
-contains the receipt from that purchase.
-
-#### payee with "NEVER CHARGED"
+#### NEVER CHARGED Payee
 
 The only exception to the standard tagging requirement is when the payee has
 been modified to indicate that the expense was `NEVER CHARGED`.  This is an