Move Graphs and Twig handling to their own Plugins
Move PDF handling to its own Plugin
Change http scheme to https

Because using dependencies via https works in the file://, http:// and
https:// schemes we have changed all dependencies to use https instead
of http.

This fixes https://github.com/phpDocumentor/phpDocumentor2/issues/1163
Merge branch 'develop' of github.com:phpDocumentor/phpDocumentor2 into develop