Fixes #157 - Add support for attaching meta data to custom filters
The MR creates a public API to filter metadata manipulations: add/set/get and the tests. If working in MV2 it delegates the calls to "adblockpluscore" functionality and hiding the errors if happen. If working in MV3 it saved the metadata details in prefs in addition to existing associated data OR delegates to "adblockpluscore" (depending on filter type).
Closes #157 (closed)
Edited by Anton Smirnov