Rethink which dependencies to install for which extras and default installation

[johann-petrak]

• need to find out which dependencies are absolutely needed for the base functionality (including pampac)
• may need to install more dependencies for base installation (default extra) than we have in the java plugin
• may need to not install some packages, e.g. anything that depends on torch to avoid version conflicts, dependency hell and give the user more control which backend package version they really want to install. Candidates for manual post-install:
  • spacy
  • stanza
  • (tner): this currently has odd installation problems, need to figure out what is going on
• also not sure what to install for notebook support by default and what to leave to user
• also, check again what is needed for dev support