Update to use the Splunk SDK 2.1

Fix for #3 

* Upgrading to use Splunk Modular Input 2.1 package.
* Adding validation logic using new o365 client method
* Adds new local directory structure matching the target app folder.
* Adding support for building SPL file automatically.
* Adding copying of app to %SPLUNK_HOME%\etc\apps\o365toSplunkDataImportApp folder