Refactoring OpenID storage code in more generic auth code

[MySQL schema change]

• The users_OpenID table become users_auth.
• This new users_auth table can contain OpenID or other auth mechanisms (we plan to add include YubiKey authentication).
• Field new names:
  • openid_id -> auth_id
  • openid_url -> auth_identity
• New fields:
  • auth_type (contains 'OpenID' for OpenID stuff)
  • auth_properties, currently NULL For configurable auth methods, can contains serialized properties

[Code change]

• Login code, settings XML file and User class updated to reflect changes
• Config change: dropped TABLE_USERS_OPENID, added TABLE_USERS_AUTH

[Misc]

• Adding cached OpenID files to .gitignore
• Cleaning extra whitespaces in code files