#3 Support sub-patch creation

[Hendrik Brummermann]

In some situation (e. g. security updates) it is desirable to create a patch based on a subset of files. But the patch needs to be compatible with an older version.

The idea is to provide the old version as baseclasspath. And the new version as plugin.jar. In addition a list of root files is provided as a set of required files.

Plugfy will check each requred file against the baseclasspath. If it is incompatible, the appropriate file from the plugin.jar is used and its name is added to the set of required files.

In the end the list of all requires files (including the root files) is printed out.