Do not insert all RSYNC paths in database

[benoit74]

Fix #220

Changes (all for the stage where we insert RSYNC result as Url into database):

• ignore all directory entries
• ignore all entries in an /old/ subfolder
• take into account the book selection which might have been passed
• display statistics after operation

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 17 lines in your changes are missing coverage. Please review.

Project coverage is 0.76%. Comparing base (59ebd30) to head (51f47f4).

Files	Patch %	Lines
src/gutenberg2zim/urls.py	0.00%	16 Missing ⚠️
src/gutenberg2zim/entrypoint.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##            main    #221      +/-   ##
========================================
- Coverage   0.76%   0.76%   -0.01%     
========================================
  Files         15      15              
  Lines       1560    1575      +15     
  Branches     336     341       +5     
========================================
  Hits          12      12              
- Misses      1548    1563      +15     

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[rgaudin]

LGTM ; please check my concern before merging