Improve handling of missing package #50
Description
When piping Get-TelligentVersion to Install-TelligentInstance, if the version doesn't exist a series of errors are reported. e.g. when calling Get-TelligentVersion 10 | Install-TelligentInstance site.name.local if no v10 package exists. We should better handle this to let the user know a package of that version couldn't be found.