Import/Export changes to allow for setting of ENABLE/SYSTEM

https://bugzilla.redhat.com/show_bug.cgi?id=1105113

The import export has been changed to support the following
1. ManageIQ domain will be automatically set to
SYSTEM=true,ENABLED=true,PRIORITY=0
2. Support for restore, during restore the ENABLED attribute from domain
yaml file will be honored.
3. PRIORITY will never be honored from the domain yaml file, it is only
used to set the import order when doing a multi domain import
4. By default for single domain imports the domain will be created as
disabled (ENABLED=false).
5. ManageIQ domain will be called ManageIQ even if IMPORT_AS=manageiq
6. During restore create the $ namespace
7. rake script allows for ENABLED=true|false
8. rake script allows for SYSTEM=true|false
@Fryguy 
http://api.rubyonrails.org/classes/Hash.html#method-i-slice
it says that "If you have an array of keys you want to limit to, you should splat them"
It works when you list it individually like you have it.