Add a bunch of shortcodes to make life easier.

These will need to be abstracted a bit to handle other stuff like libgnt,
gplugin, talkatu, etc, but this is way easier to deal with than it was.

Testing Done:
Ran locally and verified all of the Sourceforge links are working.

Reviewed at
Alan Hoskins <>
Elliott Sales de Andrade <>
Frederick F. Kautz IV <>
Gary Kramlich <>
Harrison <>
Jason Allan <>
John Bailey <>
Richard Laager <>
Robert Vehse <>
Sorvival <>
Zero <>