Add ability to filter based on mimetype and/or extension

[amcfague]

Although the current session listing allows one to filter based on the URI (and thus, extension), it might be beneficial to do this at the profiler level. For example, images, CSS, and JavaScript, are just a few of the things that will be picked up by the profiler.

There should be an option to (a) filter by file extension, and (b) filter by mimetype, including wildcards. That is, application/* should block application/x-pdf, application/word, etc..