Grant schema privileges

[elsoa-invitech]

Possible fix for #604:

You can configure the schema grant in postgresql_user_privileges array:

This will set grant for database:

    postgresql_user_privileges:
      - name: foouser              # user name
        db: bardb               # database
        privs: ALL                  # privilege
        state: present

And with this patch, you can set for the schema too:

    postgresql_user_privileges:
      - name: foouser              # user name
        db: bardb               # database
        schema: public
        privs: ALL                  # privilege
        state: present