Extraction - Speed improvements (#522) (#523)

* Extraction - Speed improvements (#522)

* Initial Plugin restructure

* Detectors to plugins. Detector speed improvements

* Re-implement dlib aligner, remove models, FAN to TF. Parallel processing

* Update manual, update convert, implement parallel/serial switching

* linting + fix cuda check (setup.py). requirements update keras 2.2.4

* Add extract size option. Fix dlib hog init

* GUI: Increase tooltip width

* Update alignment tool to support new DetectedFace

* Add skip existing faces option

* Fix sort tool to new plugin structure

* remove old align plugin

* fix convert -skip faces bug

* Fix convert skipping no faces frames

* Convert - draw onto transparent layer

* Fix blur threshold bug

* fix skip_faces convert bug

* Fix training