Move path and link_name related functions and regex patterns to a new
soc/logic/path_linkname.py module, and fix all dependencies. path/link_name
functionality is becoming the generic way to identify entities in the Datastore
in a URL-compatible way.
Replace common module with validate module. Move validation function from feed module to validate module and remove feed.py. Correct any usage of validation functions from common and feed modules into validate module.
Patch by: Pawel Solyga
Review by: to-be-reviewed