After doing all the refactoring, rename the ObjectType enum to NMPObjectType.
I didn't do this earlier to avoid problems with rebasing. But since I will
backport the platform changes to nm-1-0, this is the right time to get
the name right.
After refactoring platform, nm_platform_ipx_route_get_all() and
nm_platform_ipx_address_get_all() was broken for calling with a
non-posititive ifindex (which has the meaning: ignore ifindex).
While fixing that, also refactor the NMPCacheIdType so that it matches
better the supported id-types.
Fixes: 470bcefa5f
NMPObject is a simple "object" implemenation around NMPlatformObject.
They are ref-counted and have a class-pointer. Several basic functions
like equality, hash, to-string are implemented.
NMPCache is can be used to store the NMPObject. Objects are indexed
via their primary id, but there is also multi-lookup via NMCacheId
and NMMultiIndex.
Part of the implementation is inside "nm-linux-platform.c",
because it depends on utility functions from there.
