Added get_common_info_ratings with corresponding tests.
Improved globalNetwork, fixed bugs.
Added primitive functionality to get_extreme_info_ratings
Updated get_extreme_info_ratings plus some tests.
get_extreme_info_ratings added with desired functionality.
get_max_rating_difference now working. Bundled with tests.
Moved around some code in globalNetwork as information objects aren't supposed to be in the graph as of now.
Merge branch 'database'

Updating master with the latest database functionality.