Replaced RestoreRequest with HasPaths.

Moved HasPaths into the models package, since it's now used to build requests as well as responses.
HasPaths now has a List of path Strings, rather than just a String value listing the paths.
This also fixes error message parsing in ErrorDiskResourceMoveCategory and DiskResourceMoveCallback.
CORE-4339 Updated DiskResourceServiceFacade::download to use HasPaths.