Do not set titles on modal message dialogs, they are redundant with the contents

The GNOME HIG says: "Alert windows have no titles, as the title would usually
unnecessarily duplicate the alert's primary text."

Also remove useless icons on windows other than the primary PiTiVi window,
and change the "unsaved changes" dialog to a "question" defaulting to "Cancel".
Updated Polish translation
Updated Czech translation
Updated Brazilian Portuguese translation
Fix running installed PiTivi

track.py seems to be gone, while controls.py has been added.
Fix deprecated usage of GObject namespace for timeout and source

Fix for a second time deprecated usage of GObject namespace for timeout_add
and source_remove
Updated Spanish translation
Updated Slovenian translation
script: do not build submodules from scratch everytime
bin: Misc indentation fixes in git-environment
Updated Serbian translation
render:  Show rendering errors in a dialog

Abort rendering when an error is encountered in the pipeline,
show the error so that the user actually knows something went wrong.

Fixes bug #635874
ui/filelisterrordialog: Set the GTK box orientation to be vertical

This also updates the GtkBuilder file's syntax to Glade's latest tastes
render: Show a more human-readable message when an error occurs in the pipeline

Hide the gory details in a GTK Expander widget
Updated Polish translation
Make the dogtail tests work again with the Clutter timeline, cleanup code
mainwindow: Ensure "Clip properties" is the focused context tab on startup
previewers: Use proper debug statements instead of prints for the thumbnailer

Also rename some internal variables
previewers: General code cleanup
Updated Spanish translation