Fix tab key behavior

Fixes #7
Fix MOD + mouse press behavior

Fix MOD key value on OS X by introducing a new enum in Globals.h.

Fix #8
    The errornous behavior is caused because the loops appending left/up
    movements have wrong conditions, therefore not working properly.
Refactor View's private fields into PIMPL
Implement context menu

Fixes #2
Fix Qt 5 compatibility
Fix double click

See #11
Fix triple click on Qt 5

This and previous commit fix #11
Format fix
Better View::insertText
Reimplement preedit text holder behavior

This should fix #9 and #10 together
Merge branch 'master' into preferences

Conflicts:
	src/Qelly.pro
Compilation and runtime error fix
Remvoe dead code
Add missing emit
Comment formatting
We'll implement redraw later...