swh.web.settings: Use different setup according to platform (dev/prod)
swh.web.settings: Permit to setup the cache uri from webapp.yml
swh.web.config: Clarify setup configuration key intent
swh.web.settings: Remove throttling inhitition when in debug mode
Misc: Remove unused files from git (db.sqlite3, webapp.yml)
Related T754
please rebase before submitting diffs; this code was simplified; so you can simplify the new base YamlMapping similarly