Removing GetSites , GetSitesFRomOARParse, verify_site

Removing  GetSites , GetSitesFRomOARParse, verify_site
as Senslab only has one main entry point and is considered
as one and unique site : therfore, does not need to handle
multiple sites. May be subject to changes in the future.
Removed the peer checkings in:
verify_slice_nodes, verify_slice, for the same reason.
Removed verify_slice_links and verify_slice_attributes
(no links and no special attibutes in senslab slices).