Hygiene: Subdir ContentFixer implementations

Much like the Extractor implementations lets subdir these
to keep it separate.  Additionally the name Controller doesn't
really describe what the class does, the best name seems to be
ContentFixer.  As ContentFixer is already taken by the interface
lets rename the interface to just Fixer.

Change-Id: I350814ff0a532106fbd3d0d506fc685bbee8f0bf