Add a flexible FileFilter to decide which files to index

[bitzl]

We use OpenWayback for visual control of harvested websites. Unfortunately, the Web Curator Tool creates temporary WARC files in the same directory as the WARC files we want to view. This leads to indexed WARC files we do not want to view (the temporary ones).

Proposed solution: A new FileFilter that allows the exclusion of filenames containing a certain String. In a more flexible solution, inclusion and exclusion could be configurable via RegularExpressions.