More use of escape_sql_id().

* glom/base_db.cc:
* glom/libglom/db_utils.cc:
* glom/libglom/privs.cc:
* glom/mode_design/users/dialog_groups_list.cc:
* glom/mode_design/users/dialog_users_list.cc: Use
escape_sql_id() instead of manually adding quotes with no
escaping. However, I have not yet done this for group and
user names.