Reduce number of refreshes in FileSystem watching

The FileSystem provider was watching and invalidating on file system
changes where it did not need to invalidate.
Added "watch" to FileSystem docs

Added documentation for watch static parameter
Merge remote-tracking branch 'upstream/master'
Added common folders to main docs
Merge pull request #38 from ReedCopsey/master

Improved watching, and added docs for "watch" in FileSystem provider