Lots more tests

* Removed duration tests, as they really weren't incredibly beneficial
or informative
* Added "IsMagic" to Magic enumeration to account for other things like
wondrous items
* Change special ability data provider to return empty enumerable for
unfound ability names, instead of throwing error
* Change intelligence generator to reflect the curse generator by taking
in magic
* Added a bunch more percentile tests
* Got tests for wondrous item attributes (currently failing)