Added command line scanning support for ASI.

Made changes to the commandline parameter.
"--frequency-table atsc-vsb8-us " is broken down to "--freq-std atsc --modulation vsb8 --region us"

Scanning of atsc (ScanTypeSetting::FullScan_ATSC) , dvbt (ScanTypeSetting::FullScan_DVBT)
and mpeg (ScanTypeSetting::CurrentTransportScan) is currently supported.