Cleanup
Improved sheet selecting logic
Fixed routing to persist node uuid when browsing between sheets (periods)
Fixed errors on backward/forward navigation
Fixed closing comments pane when opened from sheet_scope_comment button
Fixed comments check for logged in user
Fixed comments in main scope, i.e. sheet's level description
Fixed comments count
Fixed comments serialization
Fixed comments' text serialization
Clean up indentation for PEP8
Fixed updating comment buttons and Item models' related attributes after comment creation
Fixed initial comment count in scope item button to be blank if 0 and not 0