Basic rpc sync method (to replace Backbone.rpc)
Replace Backbone.rpc with our own rpc sync method
Remove Backbone.rpc
Allow go.components.rpc.sync's ajax options to be overriden
Remove unnecessary options arg from go.components.rpc.ajaxOptions()
Change go.components.rpc.sync to support json rpc error responses
Merge branch 'feature/issue-522-replace-backbone-rpc' into develop-frontend