idviews: Add ipa idview-apply and idview-unapply commands

Part of: https://fedorahosted.org/freeipa/ticket/3979
idviews: Extend idview-show command to display assigned idoverrides and hosts

Part of: https://fedorahosted.org/freeipa/ticket/3979
ipalib: host_del: Extend LDAPDelete's takes_options instead of overriding

The host-del command did not accept --continue option, since the
takes_options was overriden and did not take the options from LDAPDelete.

Fix the behaviour.

https://fedorahosted.org/freeipa/ticket/4473
trusts: Add conversion from SID to object name
idviews: Support specifying object names instead of raw anchors only
idviews: Split the idoverride object into iduseroverride and idgroupoverride
idviews: Split the idoverride commands into iduseroverride and idgroupoverride
idviews: Alter idoverride methods to work with splitted objects
idviews: Change format of IPA anchor to include domain
idviews: Raise NotFound errors if object to override could not be found
idviews: Resolve anchors to object names in idview-show
ipatests: Add xmlrpc tests for idviews plugin