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
Why was this line changed?

I believe in python it's pretty common to write SQL statements as triple quoted strings because the lines can get pretty long.

http://stackoverflow.com/questions/12825140/split-a-long-sql-query-inside-a-variable
https://dev.launchpad.net/PythonStyleGuide#Multi-line_SQL