Improve includedFiles logic and logging

[simonhauck]

As discussed in this #392 the logging for included files is a bit misleading.

Also the method signature does not a good job to actually reflect what is happening.

For example: The convention value is an empty string -> The IncludedFilesParser must know that. If the list is empty -> Analyze all files (from the name I would expect that this list would always contains the files to be analyzed).