Big changes to mods and rulesets - almost production ready!

Rulesets are heavy to load so we now have a RulesetCache, which can construct "custom" rulesets with a list of mods!
We now pack mod images on Desktop run, and load the atlases for the loaded mods on load game!

android/assets/modss/myFirstMod/game.atlas

@@ -0,0 +1,13 @@
+
+game.png
+size: 128,128
+format: RGBA8888
+filter: MipMapLinearLinear,MipMapLinearLinear
+repeat: none
+UnitIcons/Maori Warrior
+  rotate: false
+  xy: 2, 2
+  size: 100, 100
+  orig: 100, 100
+  offset: 0, 0
+  index: -1