Add an aggregate stats to the plugin manager's view

[Xpirix]

• This PR is for the issue Add an aggregate stats to the plugin manager's view #39

Changes summary

• Add GeoIp to the project
• Add country_code and country_name to the model PluginVersionDownload. For existing records, the values of these fields are set to N/D (not determined)
• Create or update the record when a download request has been made
• Add a Stats tab in the plugin details page: Map of downloads per country and top download per country

Requirements

• This feature needs Metabase. There are already some open PRs that implement Metabase: Add metabase, upgrade postgis #274 or Upgrade project to Django 3/Python 3.7 #310
• Generate the dashboard in Metabase
• Add the dashboard URL to the environment variables (METABASE_DASHBOARD_URL)

Please find below a GIF for this feature:

[codecov-commenter]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (6589e3c) 81.94% compared to head (5bd44bc) 82.05%.

Files	Patch %	Lines
qgis-app/plugins/utils.py	83.33%	1 Missing ⚠️

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #331      +/-   ##
==========================================
+ Coverage   81.94%   82.05%   +0.11%     
==========================================
  Files         139      140       +1     
  Lines        5418     5457      +39     
==========================================
+ Hits         4440     4478      +38     
- Misses        978      979       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[dimasciput]

@Xpirix please fix the conflicts