Use "virStoragePoolObj" as a prefix for any external API in virstorageobj.

Also a couple of functions were local to virstorageobj.c, so remove their
external defs iin virstorageobj.h.

NB: The virStorageVolDef* API's won't change.
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>

In an effort to be consistent with the source module, alter the function
prototypes to follow the similar style of source with the "type" on one
line followed by the function name and arguments on subsequent lines with
with argument getting it's own line.
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>

Move all the StoragePoolObj related API's into their own module
virstorageobj from the storage_conf

Purely code motion at this point, plus adjustments to cleanly build
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>