Add Source command.

[Arielfoever]

Add --json specific

This fixed #eveseat/seat#802

[warlof]

Hi,

which alternative can have json argument ?
I also not fully understand the link with the issue - as I get it, the issue is talking about troubles while collecting SDE from third party platform - however, this change is altering the way to retrieve the manifest containing version and tables which need to be collected.

[Arielfoever]

@warlof Yes , Then you can control source by controlling json. If you want to download tables frome other site ,you can specific json option.