adding system property for databases as part of #36

The Hibernate config file is now settable via the system property `mamute.database`. The value defaults to the original '/hibernate.cfg.xml' value if the property is not specified.

Also added a basic configuration for running the tests with H2. The Maven build will default to using the MySQL configuration, but you can override it like so:

```
mvn clean package -Dmamute.database=h2
```
I think that your IDE messed up the indentation, can you configure it to use 4 spaces of indentation? because its hard to review your code here at github that way...

 (that's our convention, right @leocwolter?)