Install Nemoh verbosity and instructions

[rgcoe]

Per #148, we should

• More verbose error message (report what directory is being searched, what is in that directory, and which of the binaries are missing)
• If no args, use uigetdir to set Nemoh directory
• Explain in documentation how installNemoh works

[H0R5E]

We should also add in the docs that virus checkers often quarantine NEMOH files on Windows. Happens to me weekly.