Merge pull request #100 from DenisKlimenko/master

Done selection
Done issue #82
Merge pull request #101 from Gr1N/refactoring

Refactoring
Added CurveLineInstrument class & button for it (issue #103)
Refactor instrument's buttons & menu items handlers (do it as one
handler).
Add icon for cuvre & working on curve realization
Remove not needed now funcs from toolbar, remove heap alloc in
palletebutton, working on curve instrument.
Done Bezier Curve Instrument (issue #103).
Merge pull request #106 from faulknercs/master

Done Issue #103
Fix for issue #103
Added clear button to ShortcutEdit class
Fix Bezier curve bug (restore image, when change instrument & then set
again Curve instrument)
Begin refactor UndoStack
Added makeUndoCommand member-function to AbstractInstrument
Merge pull request #107 from faulknercs/master

ShortcutEdit enchance
Better file argument support for easypaint (issue #81)
Changed rotate right/left to clockwise/counter-clockwise (issue #111).
Changed autosave interval to seconds (issue #110). Edit russion translation.
Restore main window size on start
Option 'Restore window size on start' added