Make frescobaldi restartable

Solution from here:
http://stackoverflow.com/questions/15221361/how-to-restart-pyqt4-application

Seems to work, but I didn't test it with command line arguments
Add app.qApp.isGitControlled flag

This flag is True if Frescobaldi is run from the Git repository.
The used check is the presence of the .gitignore file
Only create the restart menu item when run from Git
add eventfilter capabilities to BoundaryHandler
also intercept doubleclick to select word under cursor
improve word-boundary behaviour, fix #106
Merge pull request #219 from uliska/restart-app

Make Frescobaldi restartable
make restart functionality MUCH simpler

the code was intermingled everywhere. Now it works as it should, simply
by callinp app.restart(). Added app.is_git_controlled() instead of setting
an attribute to the global QApplication object.
unneeded import
pot/po/nl
regard words with embedded hyphen as one word, e.g. system-start-delimiter
also word boundary handling in snippet edit
circumvent pyqt4/sip bug: keep ref to the highlighter in snippet/edit

if is constructed with a parent (the document() of the textedit)
but even though it is deleted by current pyqt4/sip4
pick the double backslash as a word, nicer in snippet/edit