Fix a couple of checkstyle / pmd issues.

- remove all hard tabs
- add missing braces for if / for statements
- correct modifier order to match JLS
- remove wildcard imports.
Trying to parallelize the tests.

Turns out, that Derby is a really bad database for testing because
setting it up takes quite some time. So for parallel tests, setting a
new database up every time blows the test runtime up 10x.

Switch back to using the serial tests, however this yields some clean
up around the Derby setup and teardown code and cleans up the Spring
test a bit.