core: Use OS repository instead of VmOsType

This patch is retiring VmOsType and using the backend OS info repository
pls see http://www.ovirt.org/OS_info

Engine:
* Move relevant ConfigValues to OsRepository
* Move hard-coded code that uses the VmOsType member names
* Make searchbackend injectable - different value completer for engine,UI

UI:
* Use AsyncdataProvider to query the os repository
* Use an injected auto-completer for searchbackend that uses
values queried from AsymcDataProvider
* Mode all usages in models and views to query the AsyncDataProvider
for the OS name

REST:
* change the Mapper to use the OsRepository
* for backward compatibility convert REST OS naming convention
on a unique OS name

Change-Id: I168225f20d567910cba861be75be87136926589f
Signed-off-by: Roy Golan <rgolan@redhat.com>