SCM Activity Plugin compatibility

To be compatible, we just have to remove our CxxFile and CxxDirectory implementations
and just reuse File and Directory classes. For details see:

http://sonar.15.n6.nabble.com/sonar-dev-VOTE-Sonar-Python-Plugin-0-1-td4528985.html#a4534286

To sum up: throw away some code and get a feature. Just the way I like it...

Added benefit: it should also solve SONARPLUGINS-1599 as a side effect

In order to test the SCM-Plugin compatibility do:

• install and configure the SCM plugin as described in its wiki
• run an analysis
• drill down to a file, the annotate-information on the left side should be shown

Note: as the implementation replaces CxxFile by resources.File and CxxDir
by resources.Directory the resource keys are changed which means that were breaking
the compatibility with old versions.