Major Description
Fix the TODO note in OAuth2ServiceImpl, and inject the expiration timeouts rather than reading the properties file again.
This is needed in our application as we want to use different property values for the timeouts, and at the same time really don't want to modify the shindig.properties in shindig itself, nor do we want to copy the defaults and then get bitten when shindig updates and changes/adds values.
Injection here helps us by making it possible to define those timeouts in our config file, and override the defaults inside shindig.