Reduce source code path length

Path length is too long for Windows, causing issues like:
<< [exec] error: unable to create file nuxeo-platform-directory/nuxeo-platform-directory-core/src/test/java/org/nuxeo/ecm/directory/localconfiguration/DirectoryLocalConfigurationRepositoryInit.java (No such file or directory) >>

Even under "powerful" OS where path length is not an issue, having so long paths and duplication in names is a pain.

There are a few constraints:

• it's better (even required) for an artifact to live in a directory with the same name.
• it's useful to have parent directories of SCM repositories starting with the prefix "nuxeo-".

Possible improvements:

• remove the prefix "nuxeo-" from most modules (the group is enough to know they are Nuxeo modules)
• remove the historical and now useless prefix "nuxeo-platform-" from modules
• don't repeat the path or group in the module name (for instance: "nuxeo-features-test" living in "nuxeo-features" could be simply named "test")
• reduce filenames length for the longer ones
• setup rules on file naming
• ...