Tica base class to avoid copy paste code

[marscher]

TICA and Nystroem-TICA now share a base class to avoid double implementation.

[codecov]

Codecov Report

Merging #1273 into devel will increase coverage by 0.16%.
The diff coverage is 91.5%.

@@            Coverage Diff             @@
##            devel    #1273      +/-   ##
==========================================
+ Coverage   88.17%   88.33%   +0.16%     
==========================================
  Files         223      224       +1     
  Lines       24744    24728      -16     
==========================================
+ Hits        21818    21844      +26     
+ Misses       2926     2884      -42

Impacted Files	Coverage Δ
pyemma/coordinates/tests/test_nystroem_tica.py	99.18% <100%> (+0.02%)	⬆️
pyemma/coordinates/tests/test_tica.py	99.33% <100%> (ø)	⬆️
pyemma/coordinates/transform/tica.py	90% <100%> (+1.25%)	⬆️
pyemma/coordinates/transform/nystroem_tica.py	91.97% <87.17%> (+10.72%)	⬆️
pyemma/coordinates/transform/_tica_base.py	91.39% <91.39%> (ø)
pyemma/coordinates/api.py	88.21% <0%> (+0.35%)	⬆️
pyemma/coordinates/data/util/traj_info_backends.py	92.48% <0%> (+0.93%)	⬆️

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