* Updated some unit obsoletions
* Added a missing unit upgrade
* Added some missing commas in units.json
* Replaced Military Base icon with a simpler one
The original had a bit too much detail for the size at which it is
shown.
* Enabled Arsenal and added a new Armory icon
The old icon for Armory was much more appropriate for Arsenal, so I
added a new icon for Armory instead.
* Enabled Military Base and added an icon for it
* Enabled Petra and added an icon for it
* Enabled Composite Bowman and added an icon for it
* Enabled Mobile SAM and added an icon for it
* Enabled Jet Fighter
* Made Machine Gun upgrade to Mechanized Infantry
* Removed "Will be added in G&K" comments
Since we are now targeting G&K, these comments are no longer required.
* Fixed Aluminum/Aluminium inconsistencies