removed DB matrix in travis build + introduced parametrized build for all the various DBs

well, this one is quite big, I'd like to hear from you guys if it sounds OK with you

- maven profiles refactored (benefit could be you don't need to modify pom.xml any more to run tests in your ide, as all the drivers are included by default)
- junit tests running in travis are refactored in a way, that are parametrized with env var DB that can contain multiple DBs, i.e. -DDB=MySQL,H2,HSQLDB (see travis profile)
- due to parametrized run - unregistration of drivers happen prio to each build
- initial Datasource tests introduced using arquillian. with following limitations: XA not tested yet over P6Spy, moreover I don't see a way to have multiple DataSources referenced in spy.properties (will raise ticket for this one)
- spy.properties are currently loaded in a static way, that is hard to test (we might need some refactoring here - will raise ticket here) 
- can't remember anything further right now

Btw, seems that time of the build dropped significantly with this one