Change plugin imports to from papercast.types.plugin import Class

[papercast-dev]

We currently import stuff from plugins with

from papercast.processors import ArxivProcessor, SemanticScholarProcessor

This would change to

from papercast.processors.arxiv import ArxivProcessor from papercast.processors.semanticscholar import SemanticScholarProcessor

Pros:

• Possibility to simplify static code analysis?
  • Take a look at processors/init.py and see whether this would actually simplify anything. See #9
• Maybe make it clearer where each object is coming from

Cons:

• Import statement is not as clean, importing types from several locations take up multiple lines