[BUGFIX] Only monitor files with relevant file extensions
This change adjusts the ``ClassFiles``, ``ConfigurationFiles`` and
``TranslationFiles`` file monitors to only track changes in files with
the corresponding extension (``php`` for classes, ``yaml`` for
configuration and ``xlf`` for translations).
With the fixed ``PSR-4`` support (introduced with
I9c613df54a8b650c53b4ab8e03071432e13d3c4e) we no longer determine PHP
classes from the corresponding file path and -name, but by analyzing
the contents of the file.
Because the ``Flow_ClassFiles`` file monitor watched for changes in
all files within the classes root of all packages, this could lead
to binary files being analyzed. In some PHP versions this seem to
trigger a warning.
Releases: master, 3.0