Allow clients to reuse tokens
  - removed AuthenticateJsonRestClient to use requests w/built-in cookie support
  - add an authorization adapater
  - migrate authorization utilities to adapter
Updates based on code review

  - Removed component.getAdapter for IAuthorizationTool(context) adapter construction
  - Fixed metric facade to work from UI and zendmd
  - Use extract credentials instead of extract session credentials in metric facade
Fix metricfacade failing unit tests
Merge pull request #44 from zenoss/feature/clienttokenreuse

have the client reuse tokens