Fix args4j dependency
Replace deprecated constructor
Add h2 db dependency
Add H2 db frontend tests
Implement H2 db frontend

The H2 db frontend does not support foreign keys relationships yet.
Test foreign key support for H2 db frontend
Move method refactoring
Add foreign key reference extraction
Update README
Revert "Replace deprecated constructor"

This reverts commit 8d7f94fd5aee739ea5528471e3fc62903a3dbc20.
Use args4j 2.0.27 instead of 2.0.29

Version 2.0.29 of args4j prevents gradle from building properly.
Fix typos
Handle invalid database address for H2
Merge pull request #11 from hschink/feature/h2db_support