Merge pull request #861 from rustam-azimov/feature

Кривые линки
for rustam with love
Add enum describing type of line and fixed some indentation.
Loop edges implementation added.
Merge branch 'feature' of https://github.com/VladimirGl/qreal into feature
Loop connection to one port impelmentation.
Merge branch 'feature' of https://github.com/VladimirGl/qreal into feature
Edge settings moved to the editor page.