Initial step in refactoring RainbowTagger into RainbowProvider
Separated ITagger<RainbowTag> implementation from RainbowProvider
Make provider work on HTMLX editor
Rename RainbowTagger -> RainbowProvider
Move RainbowColorTagger into separate file
Fix raising of TagsChanged event on Rainbow brances
Arrange using declarations
Merge branch 'rainbow2' into develop