Started projecttree refactoring
Started work on project tree
Added base functional treeview, reconnected opening of files and
expand/collapse storage
Merge github.com:ninja-ide/ninja-ide
Fixed bug in __add_file that prevented files from opening
Just some code deletion, committing because I need to swap computers
Merge pull request #1395 from perrito666/master

Base project tree
improves in checkers
Merge remote-tracking branch 'upstream/master'
Merge pull request #1396 from diegosarmentero/master

Improves in checkers integration
update highlighter with checkers
Merge pull request #1397 from diegosarmentero/master

update highlighter with checkers