updated managed bean to use the same CredStore for all the endpoint
beans. Changed the name of DB store to CredStoreDB. And Added new
Endpoint classes for Twitter and Dropbox.
review comments .. removed overriden methods.
Merge branch 'master' into ManagedBeanChanges
Merge pull request #352 from VimalDhupar/managedBeanChanges

updated managed bean to use the same CredStore for all the endpoint