Make arguments for launching `lightwalletd` and `zcashd` with configuration files using `cli` flags

[dannasessha]

Requesting further comments, or details to follow.

Posting here a message I've received: "Why not pass the zcashd and lightwalletd binaries to --regtest as arguments? Force a user to figure out where to get those binaries from..."

Sounds fairly reasonable to me. I could probably easily also include default values that fail if they don't find something.

[zancas]

Adding defaults is not something to take lightly. I know experienced programmers who vehemently opine that there should be no such thing as defaults.

In any event, let's NOT add defaults to any initial implementation.

[dannasessha]

10-4.

[dannasessha]

From another conversation: "enabling zingo-cli to launch zcashd and lightwalletd (properly confiured) in regtest mode would help."

[zancas]

I think the right pattern might be:

The User has to move the zcashd and lightwalletd binaries into regest in standard locations. Then when zingo-cli --regtest is invoked it simply looks in the standard spot. No need for new arguments.

[dannasessha]

I think this done with #26 !