Eliminate warnings and add default value for app_loading resource

Eliminate Warnings: Remove unused import (java.net.URI)

Eliminate Warnings: Remove unused import (java.util.Locale)

Eliminate Warnings: Remove unused import (java.util.Calendar)

Eliminate Warnings: Remove unused import (java.lang.annotation.Target)

Eliminate Warnings: Remove unused import (java.math.BigInteger)

Eliminate Warnings: Comment out unused TAG variable in AuthenticationResult.java

Add default English string value for app_loading (like we do for broker_processing).

Update README.md with info about app_loading and broker_processing string values (to be overwritten by client applications if they wish to have non-English values)