Support filtering a target of extracted files from archive

[miurahr]

Introduce two methods for SevenZipFile object.

• extract(path, targets_list): to support extracting filename filter.
• reset()

When calling reset(), internal file pointer moves to begining of archive, then worker and decompressor are recreated. You can call extract() again, if you want.

Close: #58

[codecov]

Codecov Report

Merging #64 into master will decrease coverage by 0.01%.
The diff coverage is 82.24%.

@@            Coverage Diff             @@
##           master      #64      +/-   ##
==========================================
- Coverage   83.54%   83.52%   -0.02%     
==========================================
  Files           8        8              
  Lines        2169     2209      +40     
  Branches      356      361       +5     
==========================================
+ Hits         1812     1845      +33     
- Misses        228      236       +8     
+ Partials      129      128       -1

Flag	Coverage Δ
#linux	79.65% <82.24%> (-3.2%)	⬇️
#mac	82.84% <82.24%> (+0.17%)	⬆️
#py35	79.65% <82.24%> (+0.23%)	⬆️
#py36	100% <ø> (+16.69%)	⬆️
#py37	100% <ø> (+16.69%)	⬆️
#py38	100% <ø> (+16.66%)	⬆️
#windows	100% <ø> (+19.08%)	⬆️

Impacted Files	Coverage Δ
py7zr/helpers.py	87.2% <100%> (+3.38%)	⬆️
py7zr/archiveinfo.py	83.35% <76.66%> (-0.06%)	⬇️
py7zr/py7zr.py	83.51% <80%> (-0.34%)	⬇️
py7zr/compression.py	79.35% <81.08%> (+0.04%)	⬆️

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[miurahr]

Need to write test against 1) helper.calculate_key() with flag 0x3f, 2) test with 7z(bzip2), and 3) test with unsupported algorithm(PPMd) become unexpectedly failure.