[mod] SepiaSearch: re-engineered & upgrade to data_type: traits_v1

- fetch_traits() SepiaSearch and Peertube are using identical languages.
  Replace module's dictionary `supported_languages` by `engine.traits.languages`
  (data_type: `traits_v1`).
- fixed code to pass pylint
- request(): add argument boostLanguages
- response(): is replaced by peertube's video_response() function, which adds
  metadata from channel name, host & tags

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>