feat(datasource): support external datasource urls

[aviadhaham]

still WIP, you can look if you want though :)
@orellazri

[aviadhaham]

@orellazri made some progress, as per our talk. pushed to have another check point.
I still need to create tests for web
and also see how I'm closing these files in createDatasourceFromURL func in parse.go

[aviadhaham]

@orellazri that's done, please check