enhancement: new cmdlet: Clear-SplunkIndex

[halr9000]

alias: Clean-SplunkIndex, Clean-SplunkEventData
analog to: http://docs.splunk.com/Documentation/Splunk/latest/admin/RemovedatafromSplunk

• Need way to detect if local or remote splunkd is stopped, otherwise clear commands will fail
• Integrate with stop/start splunk service cmdlets (which don't exist)?
• Parameters to indicate which index to clean, or all (accepts pipeline input)
• Obviously should support ShouldProcess (http://technet.microsoft.com/en-us/library/hh847781) with a high impact