Implements GNIP #3718 (Worldmap contrib application)

[capooti]

This PR adds the GeoNode contrib application in GeoNode.
It also include a few enhancements (like for example using u18n in a number of places)

[afabiani]

Hi @capooti great work thanks. Will test the PR ASAP on my side.
I see also a lot of effort on improving translations, very nice.

Just few comments:

1. In theory we should first commit the PR into unstable (master) and then backport to stable (2.7.x/2.8.1). Nevertheless I see that this is mostly a contrib module, so it should not affect that much the core, but I guess we need to ask the community first before including this into the 2.8.1 release. I would not break people instances. What do you think? And also, how difficult would be to port this stuff on Django 1.11?

2. Thinking out loud here, not really proposing solution... everytime we introduce contrib modules, we are somehow forced to put settings and checks on core also. This is not quite good in general architecturally speaking. We should envisage a way to really have contrib apps fully pluggable (except for real improvements/fixes/extensions to the core that are useful in general)

3. In order to fix pep8 issues, you need to do a "pip install -e . --upgrade" first. This will update flake8 and pyflakes versions.

[afabiani]

I don't quite understand why you removed a comma here. It looks to me a syntax error.

[capooti]

thanks for spotting it! I am not sure how this happened.

[codecov]

Codecov Report

Merging #3817 into 2.7.x will decrease coverage by 0.04%.
The diff coverage is 42.22%.

@@            Coverage Diff             @@
##            2.7.x    #3817      +/-   ##
==========================================
- Coverage   42.61%   42.56%   -0.05%     
==========================================
  Files         257      261       +4     
  Lines       18092    18166      +74     
  Branches     2753     2760       +7     
==========================================
+ Hits         7710     7733      +23     
- Misses       9850     9898      +48     
- Partials      532      535       +3

Impacted Files	Coverage Δ
geonode/groups/forms.py	46% <ø> (ø)	⬆️
geonode/people/forms.py	82.85% <ø> (ø)	⬆️
geonode/people/models.py	85.52% <ø> (ø)	⬆️
geonode/context_processors.py	40.9% <0%> (-59.1%)	⬇️
geonode/maps/migrations/0026_map_content_map.py	100% <100%> (ø)
geonode/layers/models.py	74.11% <100%> (ø)	⬆️
geonode/maps/migrations/0030_merge.py	100% <100%> (ø)
geonode/groups/models.py	65% <100%> (ø)	⬆️
geonode/base/models.py	74.21% <100%> (ø)	⬆️
...ode/maps/migrations/0027_remove_map_content_map.py	100% <100%> (ø)
... and 8 more

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[afabiani]

Are there instructions and documentation on how to handle those optional settings?

[capooti]

yes, I have added a page in the documentation:
https://github.com/GeoNode/geonode/blob/2.7.x/docs/reference/worldmap.txt

I will try to improve it as soon as possible.

thanks!