Added filefilter to the CheckCaseTrigger.
A filefilter is added as an additional key on the command line:
It should contain valid Perforce depot syntax lines, which are treated as
exceptions. Changed files that match any of the lines in the filefilter will
be allowed to submit even if they break the case consistency.
This is for cases where some files are Unix-specific and need to be able to
store two files or directories that only differ by case - as an exception.
Also fixed a tabbing problem in the P4Triggers.py file.