unit test and refactor database.py

Updates to ``tests/framework/test_database.py`` and ``framework/database.py``.

- Replaced ``test_database.py`` ``unittest`` references with ``pytest`` references
- Removed test methods that checked the return type of database functions
- Added test methods that checked the return values of database functions
- Modified database functions to handle python strings properly
- Added bound values to the add_presentation and update_presentation database functions.
- Removed dummy record inserted by default.

Related gh484
If I click, prepare to record -> record -> stop -> prepare to record -> prepare to record

2014-10-15 12:04:02,081 (   DEBUG) freeseer.framework.multimedia           : Loading Video Mixer Input: Desktop Source-0
2014-10-15 12:04:02,101 (   DEBUG) freeseer.framework.multimedia           : Loading Video Mixer Input: Desktop Source-1
2014-10-15 12:04:02,249 (   DEBUG) freeseer.framework.multimedia           : Gstreamer paused.
2014-10-15 12:04:05,622 (   DEBUG) freeseer.framework.multimedia           : Recording started.
2014-10-15 12:04:05,663 (   DEBUG) freeseer.framework.multimedia           : Preview loaded into window.
2014-10-15 12:04:26,873 (   DEBUG) freeseer.framework.multimedia           : Gstreamer stopped.
2014-10-15 12:04:28,747 (   DEBUG) freeseer.framework.multimedia           : Loading Output plugins...
2014-10-15 12:04:28,748 (   DEBUG) freeseer.framework.multimedia           : Loading Output: Video Preview
2014-10-15 12:04:28,773 (   DEBUG) freeseer.framework.multimedia           : Loading Video Recording plugins...
2014-10-15 12:04:28,773 (   DEBUG) freeseer.framework.multimedia           : Loading Video Mixer Input: Desktop Source-0
2014-10-15 12:04:28,788 (   DEBUG) freeseer.framework.multimedia           : Loading Video Mixer Input: Desktop Source-1

(__main__.py:19363): GStreamer-WARNING **: Name 'mainsrc_scale' is not unique in bin 'player', not adding
Traceback (most recent call last):
  File "freeseer/frontend/record/record.py", line 351, in standby
    if self.load_backend():
  File "freeseer/frontend/record/record.py", line 553, in load_backend
    initialized, self.recently_recorded_video = self.controller.load_backend(presentation)
  File "freeseer/frontend/record/RecordingController.py", line 58, in load_backend
    initialized, filename_for_frontend = self.media.load_backend(presentation)
  File "freeseer/framework/multimedia.py", line 273, in load_backend
    if not self.load_videomixer(videomixer, videomixer_inputs):
  File "freeseer/framework/multimedia.py", line 357, in load_videomixer
    mixer.load_inputs(self.player, self.videomixer, inputs)
  File "/home/kalen/Work/Repositories/freeseer/src/freeseer/plugins/videomixer/pip/__init__.py", line 123, in load_inputs
    map(lambda element: player.add(element), mainsrc_elements)
  File "/home/kalen/Work/Repositories/freeseer/src/freeseer/plugins/videomixer/pip/__init__.py", line 123, in <lambda>
    map(lambda element: player.add(element), mainsrc_elements)
gst.AddError: Could not add element 'mainsrc_scale'