CN-26: 3 columns layout
CN-26: Very first layout basic support
CN-26: Added layers delete
CN-26: Added switching layers' position
CN-26: Little refactor, fixed bug with active layers when changed
git now ignores logs; updated submodule assets
CN-26: Big refactor, changed classes responsibilities and abstraction level
CN-26: Added ability to remove bottom layer, but only if it's not the only one
CN-26: Fixed bug with deletion of a layer with lower index than the active
CN-26: Grid is again the same size as canvas
CN-26: Editor element optimalizations
Merge branch 'develop' into CN-26

Conflicts:
	app/styles/style.scss
Merge pull request #3 from BKM-team/CN-26

CN-2: Added layers support