Fix printing of version in the generated configure/build/install scripts

[wdeconinck]

In ecbundle/build.py the ecbundle_version string was not printed in the generated configure.sh, build.sh, install.sh scripts.
This PR fixes that and places the __version__ string in a dedicated version.py file.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 40.67%. Comparing base (468b73c) to head (335fd61).

Files with missing lines	Patch %	Lines
setup.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop      #37      +/-   ##
===========================================
+ Coverage    40.66%   40.67%   +0.01%     
===========================================
  Files           48       49       +1     
  Lines        10129    10131       +2     
===========================================
+ Hits          4119     4121       +2     
  Misses        6010     6010              

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