Exposing filter functions for easier overrides
Merge branch 'master' into expose_filter_functions
Revert "Exposing filter functions for easier overrides"

This reverts commit baa154e28be4f760f28b07881b2409666ff17872.
Merge branch 'master' into expose_filter_functions
Changes to reflect Gordon's proposal for exposing chart filtering
Added hasFilterHandler.  Added code documentation
Merge branch 'master' into expose_filter_functions
Added tests for filter changes
Merge pull request #557
clarify test names

"has x" in the current tests means dc should already have x
"with x" means we are trying plugging in x