Move oak-it-osgi to top level

The oak-it module only contains the single oak-it-osgi module, which in turn consists of a single test class.

I suggest to at least move oak-it-osgi to the top level reactor to be consistent with the flat module hierarchy we adopted. IMO an even better solution would be to move the single test class to oak-run. Not sure whether this is viable though due to the custom assembly necessary.