Move refresh_objects into a manage.py command

refs #16203
Installation Docs: Add new refreshcache command instructions

refs #16203
Merge branch 'bug/16203' into release/0.11

* bug/16203:
  Installation Docs: Add new refreshcache command instructions
  Move refresh_objects into a manage.py command
wsgi.py: Remove unnecessary additional paths
Move novnc from root folder into static folder
settings/base: Remove novnc from STATICFILES_DIRS

No longer necessary with novnc in our static files folder.
manage.py: Use full package path to settings
Move setup.sh and build_wheels.sh into main gwm repo.
Rework settings.

Settings are use the following precedence:
base.py is the defaults, then /opt/ganeti_webmgr/config.yml is read and it's
settings are used. Finally settings.py is used, if it exists.

Each settings file does not wipe settings from previous files, only
overriding settings it's defined itself.
Fix an error in base.py. Update setup script.

Add pyyaml to requirements
settings/base: Use full python module path to django apps
settings/base: Add more require settings as defaults
Rewrite all imports to import from ganeti_webmgr module.

To make this into a proper python package, and to use django-admin.py this is
necessary. We can now import any of ganeti_webmgr's modules and not worry about
pythonpath.
Use fully qualified imports for custom fields

Had to update migrations in order for the migrations to access custom fields
Use fully qualified module in urls
Update refreshcache to use fully qualified imports.