Extend ALM and BCFW documentation and add Multi-Threading

[JannisHal]

• Add BCFW documentation example
• Revise ALM example to stress the difference to BCFW
• Add Multi-Threading to BCFW
• Additional tests for BlockVector
• Smaller fixes of typos etc.

[codecov]

Codecov Report

Attention: Patch coverage is 85.71429% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 86.82%. Comparing base (3503392) to head (3ba6a6c).
Report is 7 commits behind head on master.

❗ Current head 3ba6a6c differs from pull request most recent head ae9fbce. Consider uploading reports for the commit ae9fbce to get more accurate results

Files	Patch %	Lines
src/block_oracles.jl	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #463      +/-   ##
==========================================
+ Coverage   84.71%   86.82%   +2.10%     
==========================================
  Files          22       21       -1     
  Lines        2879     2778     -101     
==========================================
- Hits         2439     2412      -27     
+ Misses        440      366      -74     

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