Falsecolor

[norihiro]

This is a new implementation of false color as a source and a filter, and adding it to the dock.

TODO:

• [ ] Does the false color assignment depend on color space?

Generic checklist

• [ ] The commit is reviewed by yourself.
• [x] The code is tested.
• [x] Document is up to date or not necessary to be changed.
• [x] The commit is compatible with repository's license.