Generate a smaller Bugzilla component .json file

Current situation: php generates the web/cache/bugzilla_components.json
file if missing or older than a week, current size 9.5MB

Solution:
* move generation of this file to a python script (bugzilla_query.py)
and call it at the end of glossaire.sh if the file is missing or older
than a week
* strip the file from all unnecessary information, but maintain the
same structure of the original. If for any reasons the file is missing,
php can still generate the gigantic file

Resulting file: 7 kB

I've also remove web/bugzilla_components.txt since I can't find any
reference.
Merge pull request #143 from flodolo/light_bugzilla

Generate a smaller Bugzilla component .json file