Create LWJGL EngineSubsystem
Replace Iterable with a Deque for engine subsystems
Added beginnings of inventory screen.
Improved rendering of mesh in UI.
Added commands to reload shaders and materials.
Merge branch 'develop' into nui

Conflicts:
	engine/src/main/resources/assets/skins/default.skin
Added tooltips to inventory cells.
Merge branch 'develop' into nui
Added stack count display to inventory cell.
Added support for blocks upon destruction automatically spewing their contents.
Added additional events to query and cancel delayed actions.
Fixing rendering of non-16x16 icons, both in inventory, as well as in mesh form.
Fixing rendering of dropped blocks and allowing alpha channel on item Meshes.
Removed the doubled remove from set call.
Fixing hilarious bug in the Region3i.
Items can now be dropped in multiples, not just one per object in world. Fixing bugs in automatic dropping from entities with InventoryComponent.
Merge pull request #878 from MarcinSc/develop

Support for non 16x16 icons.
Ability to query and cancel events.
Support for dropping all items on destruction of a block with inventory.
Merge branch 'develop' of git@github.com:MovingBlocks/Terasology.git into nui
Mesh generated for icons scales properly with their size.
Tiny bug fix - don't scan for sub classes in modules without code
Fix for: NUI - modules should activate/deactivate on double-click #845
Merge pull request #883 from JoeClacks/develop

Fix for: NUI - modules should activate/deactivate on double-click #845