Slim public API; remove properties

[jsmariegaard]

Removed properties:

• Comparer
  • quantity_name
  • obs
  • mod
  • obs_name
  • _unit_text
• TimeSeries
  • color (temporary disabled until we have better color handling)
  • plot.plot (no need for a ts.plot.plot() - it's ugly 🤢)

Apart from this lots of docstring improvements and fixing broken links in docs.

[ecomodeller]

• plot.plot (no need for a ts.plot.plot() - it's ugly 🤢)

Fixed already in #347 ... just saying