Update mobileAnalyticsSample.html

Five changes:

-Added code comments to initial instantiation of Apigee.MonitoringClient

-Changed apiUrl in MonitoringClient instantiation to URI. apiUrl was used in a previous version of the SDK, but has since been changed to URI.

-Pre-populate orgName and appName fields with the value of orgName and appName vars

-Changed url var (line 47) to use monitoringClient.URI instead of static URL

-Auto-update MonitoringClient whenever value of appName or orgName field changes. This includes:

-Setting monitoringClient.orgName and monitoringClient.appName

-Re-download apigeeMobileConfig with downloadConfig() so that 'Log a Message' feature works properly

-Re-start session with startSession() so that session data is captured for the right org/app.