Inlined normalizeXRI
Simplify getLocalID.
Removed unnecessary import aliases.
Don't keep display_identifier on an endpoint.

- replaced self.display_identifier with self.iname
- renamed getDisplayIdentifier() to display_id()
- simplified conditional returns along the way.
Removed book-keeping attribute used_yadis.

It was always used to test its own correctness.
Extracted service types to the module level.
Clearer logic in getOPorUserServices
Removed compatibility implementation of enumerate.
Test correct ordering of services by type.
Inline and greatly simplify arrangeByType
Return all IDP-type services from getOPOrUserServices
Removed a pure delegating method: fromXRDS
Avoid extra parse of XRDS document in applyFilter
Inline normalization logic from discoverURI into normalizeURI
Simpler and more correct normalizeURL
Inline discoverYadis
Replace yadis DiscoveryResult with (text, xrds).
Pass already aprsed XRDS to applyFilter in discover.
Return raw data in an exception attribute after failing to parse it as XRDS.
Import only plain etxrd module in discover.py