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
```
>>> print QDateTime().currentDateTime().toString(1)
2014-11-23T23:45:49
>>> print QDate().currentDate().toString(1)
2014-11-23
```

The first timestamp command looks the most similar to the csv, 2010-05-14T10:45

The following is the only indication I could find as to what the timestamp is supposed to look like, but this is the csv/rss timestamps. Does the rest of Freeseer use something different at all?
```
	if not presentation.date and presentation.startTime and len(presentation.startTime) == 16:
            presentation.date, presentation.startTime = presentation.startTime[:-6], presentation.startTime[11:]
```