Do not log an ERROR-level exception when a user's session has timed out

See https://talk.openmrs.org/t/openmrs-apiauthenticationexception-on-simple-dry-run/3857

If a non-authenticated user tries to access a page (either because they followed a bookmark, or because their session has timed out) we log an ERROR-level exception like this:

ERROR - uncaughtException_jsp._jspService(425) |2015-12-03 23:25:23,165| Exception was thrown by not authenticated user
org.openmrs.api.APIAuthenticationException
	at org.openmrs.module.appui.UiSessionContext.requireAuthentication(UiSessionContext.java:121)
...

This is a common non-error thing to happen.

To Dos:

• Don't log the full stack trace in this situation, but just a one-liner like "Unauthenticated user tried to access $page"
• Log this at INFO level, instead of ERROR level.