Set Java version to 7

Especially in order to avoid test related code in the production environment. (see legacy/trac#12869 (moved) about util.Time).

I currently cannot point to an exploit or similar, but having something (non-static) standing in between java.lang.System.millisec and the application does not feel right.

So, a Mocking Framework might be a way to solve this. The framework should be compatible with the Guidelines.

(I could look into it. So, I have a reason to study the Guidelines thoroughly.)