Support so print can print only important text.
SVG modified to use display:inline/none based on overlay True/False and
a symlink to make it easy to change to a completely seperate svg if that
is not optimal.
SVG added layers to split text and graphic so graphics can be easily
hidden and printed.
Closes: #38
* Switch to showing the PNG version by default, as this reflects what
will actually be rendered and sent to the printer
* Include the greyscale filter
* Include the twemoji font we'll use for rendering the badges
* Company names had a misspelled filter and weren't being displayed
* Add some conditional logic so that company names don't get shown for
hobbyists or students
* Add a greyscale filter to text for more accurate preview
* Always default to SVG preview as it's the most accurate (cairo
doesn't do a great job of handling custom fonts when it converts to
png/pdf)
* Always use roboto font.
* Undo some of the debugging done early in this series of patches
* Add ability for a user to preview their own badge
* Add a template for the LCA2018 badge
