Fix #537 Translations do not work for RecordTool and ConfigTool

Calling self.app.installTranslator seems to allow the translations to go
through to the 3 apps.

Signed-off-by: Thanh Ha <thanh.ha@alumni.carleton.ca>
Update translation files

Signed-off-by: Thanh Ha <thanh.ha@alumni.carleton.ca>
Update en_US translation file strings

Signed-off-by: Thanh Ha <thanh.ha@alumni.carleton.ca>
Update resources

Signed-off-by: Thanh Ha <thanh.ha@alumni.carleton.ca>
Switch to pytest as our test runner

http://pytest.org/ for more information. Old tests done in the
traditional unittest style will continue to function.
Fix #444 Separate recording logic from the concept of a talk/presentation

- Add filename parameter to load_backend function in RecordingController
- Add metadata parameter to load_backend function in Multimedia
- Disable Record button and set tool tip when no presentations are available
- Prepare record_name and metadata in RecordingController and add
  extension to file name in Multimedia
- Change convenience commands to call load_backend from RecordingController