Update versions in pom.xml and documentation after 0.5.1 release

[github-actions]

• Versions are updated in pom.xml, README.md and in examples
• Current project version is incremented to the next snapshot

[codecov]

Codecov Report

Merging #850 (5f3345e) into master (19b838d) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #850   +/-   ##
=========================================
  Coverage     81.05%   81.05%           
  Complexity     2284     2284           
=========================================
  Files           100      100           
  Lines          5847     5847           
  Branches       1813     1813           
=========================================
  Hits           4739     4739           
  Misses          286      286           
  Partials        822      822           

Flag	Coverage Δ	Complexity Δ
unittests	81.05% <ø> (ø)	2284.00 <ø> (ø)

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