Use htmldataprocessor to refactor pasting clean up

[Garry Yao]

We should start using htmldataprocessor when dealing with the pasting input, instead of current implementation which based on regexp exclusively, such a infrustructure would bring benefits in many sense:

1. Allow structure transformation to happen easily toward the source instead of simply cleanup, e.g. MS-WORD created middot bullet -> HTML unordered list;
2. Leveraging all the existing rules we currently have for output, e.g. flash object, namespaces tags;
3. It will be much more easy for developer to extend/customize by adding/altering the rules.