Move parsing functions to pkg/parsers and the specific kernel handling
functions to pkg/parsers/kernel, and parsing filters to
pkg/parsers/filter. Adjust imports and package references.

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
Merge pull request #7286 from erikh/parsers

Move parsing functions to parsers/ and the specific kernel handling...