Module json2: allow to call another search method

[vindarel]

this is an api endpoint (Module.json2) that searches with a regular
database query (not Whoosh). Some modules may want to have their own
search method (so as to add bonus information into the text results for
example), so we call it if any or we rely on the basic
search (name.ilike).

[codecov-io]

Codecov Report

Merging #38 into master will decrease coverage by <.01%.
The diff coverage is 18.18%.

@@            Coverage Diff             @@
##           master      #38      +/-   ##
==========================================
- Coverage    63.6%   63.59%   -0.01%     
==========================================
  Files         136      136              
  Lines       12044    12054      +10     
==========================================
+ Hits         7660     7666       +6     
- Misses       4384     4388       +4

Impacted Files	Coverage Δ
abilian/web/frontend.py	66.51% <18.18%> (-0.32%)	⬇️
abilian/web/views/object.py	35.52% <0%> (-0.11%)	⬇️
abilian/web/tags/admin.py	34.59% <0%> (+1.68%)	⬆️

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[coveralls]

Coverage decreased (-0.01%) to 63.59% when pulling 1b49689 on json2-search-method into 4f7e2fb on master.

[coveralls]

Coverage decreased (-0.01%) to 63.59% when pulling 1b49689 on json2-search-method into 4f7e2fb on master.

[coveralls]

Coverage decreased (-0.002%) to 63.598% when pulling 5efd2b7 on json2-search-method into 4f7e2fb on master.

[coveralls]

Coverage decreased (-0.002%) to 63.598% when pulling 5efd2b7 on json2-search-method into 4f7e2fb on master.

[coveralls]

Coverage decreased (-0.002%) to 63.598% when pulling 5efd2b7 on json2-search-method into 4f7e2fb on master.

[coveralls]

Coverage decreased (-0.005%) to 63.596% when pulling 2f3630f on json2-search-method into 4f7e2fb on master.

[coveralls]

Coverage decreased (-0.01%) to 63.59% when pulling e0d27b1 on json2-search-method into 4f7e2fb on master.

[coveralls]

Coverage decreased (-0.01%) to 63.59% when pulling e0d27b1 on json2-search-method into 4f7e2fb on master.