Fix settings to work with new gwm-manage.py

Additionally: got rid of end_user.py.dist by renaming it to settings.py

refs #15105
Remove secret key from end_user.py.dist
Reverted settings.py.dist, fixed importing issue
Fixing MANIFEST.in

Someone said: "every Python project has fixing MANIFEST.in commit".
GWM is not worse!
setup.py: install package data

Package data is: templates, static files, translations, etc
Move settings around in settings.py.dist
Change manage.py reference to settings
Merge branch 'pbanaszkiewicz-bug/15105' into develop

* pbanaszkiewicz-bug/15105:
  Change manage.py reference to settings
  Move settings around in settings.py.dist
  setup.py: install package data
  Fixing MANIFEST.in
  Reverted settings.py.dist, fixed importing issue
  Fix settings to work with new gwm-manage.py
Docs: Updated installation instruction for devs
Ignoring: settings files (.gitignore in their dir)

I put .gitignore in directory containing settings files, which ignores
non-dist versions of settings for both "normal" and LDAP setting files.
Getting rid of mentions of 'end_user.py'
Merge branch 'pbanaszkiewicz-fix_documentation_15105' into develop

* pbanaszkiewicz-fix_documentation_15105:
  Getting rid of mentions of 'end_user.py'
  Ignoring: settings files (.gitignore in their dir)
  Docs: Updated installation instruction for devs