Added gst _sampler and _synth backend

GStreamer can now also handle sound requirements of sample and synth
elements

Conflicts:
	openexp/_sampler/gstreamer.py
	openexp/_synth/gstreamer.py
Updated docstrings

All docstrings now simply point to those of the legacy backends
Add temporary xpyriment-gst backend setting
Fixed freezes on Linux

changed self.experiment.sleep() calls to time.sleep() as the latter
appear not to mess up multithreading
Merge branch 'playground' into soundbackends
Add German translation
- Bump to 2.8.3~pre1
- Recompile other translations
- Switch to lrelease-qt4
Update translation files
Update advanced settings in loop (closes #263)
Fix canvas.arrow() docstring
canvas.text_size() respects line breaks and formatting (fixes #262)
Add Russian translation
- Update debian/changelog
- Update debian/copyright
Various improvements to file saving
- Don't handle exceptions while saving differently in debug mode
- Avoid chunking of extensions (closes #265)
- Warn when saving in `.opensesame` format when there are files in the file pool (closes #266)
- Use backslash filenames on Windows (closes #267)
Various improvements to file saving
- Don't handle exceptions while saving differently in debug mode
- Avoid chunking of extensions (closes #265)
- Warn when saving in `.opensesame` format when there are files in the file pool (closes #266)
- Use backslash filenames on Windows (closes #267)
Minor conflict resolution
Bump to 2.9.0~pre1
Add the quick-open-item dialog
Polish quick-open-item dialog
- Add uniform component classes
Migrate dialogs to uniform framework
- Convert sketchpad_dialog
- Convert new_loop_sequence_dialog
- Remove replace_dialog (deprecated since QProgEdit)
Further implementation of base_dialog and base_widget framework
Convert variable inspector to base_widget framework