Add a new filter for Blazar and BLLac

[JulienPeloton]

IMPORTANT: Please create an issue first before opening a Pull Request.
Linked to issue(s): Closes #164

What changes were proposed in this pull request?

New filter for Blazar and BLLac from SIMBAD (plus candidates).

[codecov-commenter]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (40b3df7) 70.14% compared to head (add0cc2) 70.27%.

❗ Current head add0cc2 differs from pull request most recent head 75c7f0a. Consider uploading reports for the commit 75c7f0a to get more accurate results

Files	Patch %	Lines
fink_filters/filter_blazar/filter.py	76.92%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #165      +/-   ##
==========================================
+ Coverage   70.14%   70.27%   +0.12%     
==========================================
  Files          18       19       +1     
  Lines         670      683      +13     
==========================================
+ Hits          470      480      +10     
- Misses        200      203       +3     

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