Cleanup of current API including type annotations

[eileen-kuehn]

This PR focuses on getting a stable API, this includes:

• adding proper type annotations,
• cleaning private/public methods
• removing unnecessary code.

[codecov]

Codecov Report

Merging #31 into master will increase coverage by 2.91%.
The diff coverage is 56.89%.

@@            Coverage Diff             @@
##           master      #31      +/-   ##
==========================================
+ Coverage   33.81%   36.73%   +2.91%     
==========================================
  Files          15       14       -1     
  Lines         686      716      +30     
  Branches      104      110       +6     
==========================================
+ Hits          232      263      +31     
+ Misses        443      433      -10     
- Partials       11       20       +9

Impacted Files	Coverage Δ
lapis/controller.py	0% <0%> (ø)	⬆️
lapis/pool_io/machines.py	0% <0%> (ø)	⬆️
lapis/monitor/cobald.py	0% <0%> (ø)	⬆️
lapis/scheduler.py	0% <0%> (ø)	⬆️
lapis/monitor/general.py	58% <0%> (+2.44%)	⬆️
lapis/drone.py	61.16% <100%> (+1.16%)	⬆️
lapis/job.py	76.78% <100%> (+0.42%)	⬆️
lapis/job_io/htcondor.py	83.33% <75%> (-6.67%)	⬇️
lapis/job_io/swf.py	84.37% <75%> (-6.54%)	⬇️
lapis/pool_io/htcondor.py	73.68% <75%> (-3.24%)	⬇️
... and 1 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update b13a2d0...ef1dfe7. Read the comment docs.

[eileen-kuehn]

Contents are handled in #101.