Generated unit tests should use same package names as the parts they test

[cyrille-artho]

The unit tests in src/test should reflect the package hierarchy in src/main. Currently, there are example models in src/test/scala/modbat/{test,examples}, but the unit tests that use them are in src/test/scala/modbat/mbt. They should be moved to the other two directories, and renamed if needed.

[cyrille-artho]

Probably the best approach is to do examples semi-manually, by looking at which files go there, and do the rest at the end in one bunch (they all go to src/test/scala/modbat/test).

[cyrille-artho]

Decided to keep the package names, as the separation into test and examples is a bit arbitrary from a testing point of view (the separation is only for documentation/distribution), and there is in fact no package modbat.test or modbat.examples in the main code; the main functionality is in modbat.mbt.