Supporting input from stdin or forwarding it to an ssh device

[Paiusco]

Requests: intel#74 intel#123

The main request is to make sure bmaptool would accept other input/output location, such as piping it from stdin and also being able to push the wic file towards an ssh device.

NOTE: I can give more info about intel#123, as it was my use-case, but also wanted to pull the other request I mentioned as a reference.