Adding item serialization/deserialization tests.

Closes #71
Clean java warnings on DataManager tests.

Some of the data manager tests had warnings and include errors from previous merges. Resolving and cleaning all of these.
Merge pull request #135 from Mobius5150/serializationtests

Adding item serialization/deserialization tests.
Merge pull request #138 from Mobius5150/cleantests

Clean java warnings on DataManager tests.