entity template system - create template, create instance, save/load, ui
entity templates share properties
adding component to entity template add it to all instances
entity template serialization is reentrant
create entity template instance in the main menu
undo/redo - closes #13
remove component
new renderable uses empty slots if available
add component command
add entity command
the position of a brush and its size are sent to the terrain's shader
missing tab - review update
Merge pull request #261 from nem0/stuff

Entity templates and undo/redo