more tidy-up and some bug fixes

The attached patch does the following:

• adds the ability to parse error responses from Google
• removes the majority of calls to drupal_set_message() calls as this is a framework/api module. The calling module should be responsible for printing messages to the screen if necessary. They may not want it in every scenario, e.g. bulk updates of accounts
• fixes some bugs due to hard-coded domain names in the urls and those still containing the 'domain' placeholder string!
• adds hashFunctionName to list of args when creating account

Dependent on #685606: coding style cleanup, #685670: modularlize the code and #685782: admin UI tidy up being applied first.