Fix some issues

[kasyanovse]

• Fix #229
• Fix #173
• Fix potential problem with n_jobs. It may appear if some multiprocessing modules cannot work with n_jobs < 0. Now n_jobs is checked and converted to positive value in GraphRequirements
• Fix problem with retaining composing time calculation. Initial generation is taked as full generation, but it does not consume any time for preparing. Also fixed problem with generation num increment.

[aim-pep8-bot]

Hello @kasyanovse! Thanks for opening this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file test/unit/test_logger.py:

Line 131:5: F631 assertion is always true, perhaps remove parentheses? Line 132:5: F631 assertion is always true, perhaps remove parentheses?

[maypink]

поменяй плиз версию голема в этих файлах на 0.4.0

[codecov-commenter]

Codecov Report

Merging #230 (0c8ed59) into main (29cd362) will decrease coverage by 0.20%. Report is 1 commits behind head on main. The diff coverage is 95.83%.

@@            Coverage Diff             @@
##             main     #230      +/-   ##
==========================================
- Coverage   72.16%   71.96%   -0.20%     
==========================================
  Files         135      136       +1     
  Lines        8061     8130      +69     
==========================================
+ Hits         5817     5851      +34     
- Misses       2244     2279      +35     

Files	Coverage Δ
golem/core/adapter/adapt_registry.py	94.59% <100.00%> (ø)
golem/core/dag/graph_utils.py	97.29% <100.00%> (ø)
golem/core/dag/linked_graph.py	98.62% <100.00%> (ø)
golem/core/dag/linked_graph_node.py	97.61% <100.00%> (ø)
golem/core/log.py	89.34% <100.00%> (-1.64%)	:arrow_down:
golem/core/optimisers/advisor.py	88.88% <100.00%> (ø)
golem/core/optimisers/fitness/fitness.py	86.90% <100.00%> (ø)
golem/core/optimisers/genetic/evaluation.py	94.00% <100.00%> (-0.38%)	:arrow_down:
...ore/optimisers/genetic/operators/base_mutations.py	90.81% <100.00%> (ø)
...lem/core/optimisers/genetic/operators/crossover.py	92.78% <100.00%> (ø)
... and 27 more

... and 4 files with indirect coverage changes