Add userClass attribute for hosts

This new freeform host attribute will allow provisioning systems
to add custom tags for host objects which can be later used for
in automember rules or for additional local interpretation.

Design page: http://www.freeipa.org/page/V3/Integration_with_a_provisioning_systems
Ticket: https://fedorahosted.org/freeipa/ticket/3583
Fix syntax of the dc attributeType

dc syntax is changed from Directory String to IA5 String to conform
to RFC 2247.

Part of the work for https://fedorahosted.org/freeipa/ticket/3578
Fix syntax errors in schema files

- add missing closing parenthesis in idnsRecord declaration
- remove extra dollar sign from ipaSudoRule declaration
- handle missing/extraneous X-ORIGIN lines in 10-selinuxusermap.update

This does not use the schema updater because the syntax needs to be
fixed in the files themselves, otherwise 389 1.3.2+ will fail
to start.
Older DS versions transparently fix the syntax errors.

The existing ldap-updater directive for ipaSudoRule is fixed
(ldap-updater runs after upgradeconfig).

https://fedorahosted.org/freeipa/ticket/3578