Try different chaining method

Added MimicFilter which mimics some filter, and can be easily made to
mimic another filter. Using this instead of SourceFitler makes it
possible to easily replace all occurrences of it.

This supersedes the Filter.Append method and all related methods.
Revert "Make LoadSettings(), SaveSettings() abstract."

This reverts commit c5a318ff6ab1f667ff1733aec1e181f7720aeab5.
Merge pull request #21 from Shiandow/work

Work
Merge pull request #22 from zachsaw/work

Merge from Shiandow:work