Modify Invoke-ReportExecution.ps1 to dump output in csv format

[RaajeevKalyan]

Default to output in csv for parity with Python script
Add optional parameter for filename (csv) and dump to file
For the Powershell code current output is to a table - that can be an optional parameter for output format (default being csv) - filename can be ignored if user chooses output format of "table" and still provides a csv filename