testedbyMetadata.bin is created in current directory

[maeste]

testedbyMetadata.bin is created in current directory. It could be better to
create it under target directory. Of course it will be cleaned when you
invoke mvn cleaned. This fact has pluses in some case (for example when some
classes has been removed and the repository should be generated), but it
have the minus that we are loosing the history.
At the moment it is the only choice possible IMHO, since keeping the history
while we maintain a repository able to run consistently test classes would
need a lot of work in the core for repository maintenance algorithm.

This issue have works both in the core and maven plugins.