python3: update build

* set python version to 3.4.0
* (HACK) add m to python include and link
python3: apply 2to3
python3: logger string/bytes convertion
python3: port more strings

* convert cairo masks to bytestring
* split string unstatically
* fix "Unicode-objects must be encoded before hashing"
* don't encode string for gtk
python3: port coptimizations renderer module
python3: apply 2to3 to tests

* fix test imports from 2to3
python3: fix tests
tests: Make the 'mock missing' reported error more readable
medialibrary: Use proper API to get uris from dragging context
medialibrary: Do not sanitize URIs it is not needed aymore

This broke after the pass to the py2to3 script and we actually do not
need it as we are now using DragContext.get_uris() to get the URI
and this provide us with a clean list of ready to be used URIs
loggable: Windup the stack leads to wrong frames
mainwindow: Replace the menubar and main toolbar by HeaderBar and MenuButton

Fixes bug #708375
Depends on GTK+ 3.10

This commit removes any dependency on GTK actions for the main window. It also
changes translatable strings and moves the "screenshot" feature to mainwindow.
dogtail: Fix some
mainwindow: Allow pressing F10 for opening the app menu
Make Pitivi a GtkApplication

Fixes https://bugzilla.gnome.org/show_bug.cgi?id=693291
Use Gio.SimpleActions to handle global app keyboard events
dogtail: Use keyboard combos to workaround unsniffable popup menu
dogtail: Fix test_timeline.py:TimelineTest.test_multiple_drag
dogtail: Fix test_timeline.py:TimelineTest.test_split
dogtail: Update timeline tests to use the new getTimelineX/Y methods