fscache plugin: Add new plugin for Linux' file-system based caching framework.

fscache plugin: Add new plugin for Linux' file-system based caching framework.

Tried to submit the patch via "git send-mail" but I don't think it worked if
you already have the patch disregard the attachment.

Looking forward to your feedback, I am sure there are a few issues its been a
few years since I programmed in C. I have been running this in my test lab at
work for a few days now with no issues.

With 62 metrics I would like to modify the code to group them by their
classification and possibly add configuration support. If the changes are
finished this weekend is it ok to send an updated patch?

Thanks
Edward

Signed-off-by: Edward "Koko" Konetzko <konetzed@quixoticagony.com>
Signed-off-by: Florian Forster <octo@leeloo.lan.home.verplant.org>