Feature request - Allow global "all orgs" added

[gregwjacobs]

At present AUTH_LDAP_DEFAULT_SENTRY_ORGANIZATION=='foo' can be used to have a user added to a single org when they login. Systems with multiple organisations would benefit from the following extension of this feature.

Ideally this feature can accommodate two additions usage modes:

AUTH_LDAP_DEFAULT_SENTRY_ORGANIZATION==['foo', 'bar', 'alice']

Join all users to the three orgs in the list above

AUTH_LDAP_DEFAULT_SENTRY_ORGANIZATION=='*'

Join all users to all orgs configured in system (wildcard)