Feature/custom regex for index parsing

[MKoesters]

Fix bugs when parsing files with non numerical id

• if groups in id can't be machted, return empty id_dict
• if first scan is not an integer, set first scan to 0
• remove debug print function
• if no integer in spec_id, return full id string

[codecov[bot]]

Codecov Report

Merging #224 into dev will increase coverage by 0.16%. The diff coverage is 69.84%.

@@            Coverage Diff             @@
##              dev     #224      +/-   ##
==========================================
+ Coverage   83.99%   84.15%   +0.16%     
==========================================
  Files          32       32              
  Lines        3673     3698      +25     
==========================================
+ Hits         3085     3112      +27     
+ Misses        588      586       -2     

Impacted Files	Coverage Δ
pymzml/spec.py	76.98% <29.41%> (+1.88%)	:arrow_up:
pymzml/file_classes/standardMzml.py	69.60% <76.66%> (-0.08%)	:arrow_down:
pymzml/file_interface.py	93.54% <100.00%> (+0.21%)	:arrow_up:
pymzml/regex_patterns.py	100.00% <100.00%> (ø)
pymzml/run.py	86.04% <100.00%> (-3.43%)	:arrow_down:
tests/main_reader_test.py	99.37% <100.00%> (-0.02%)	:arrow_down:
tests/ms2_spec_test.py	98.14% <100.00%> (+0.14%)	:arrow_up:

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