Neu3: commandline option to prevent saved protocols from starting

[olbris]

Some users want to use Neu3 to do unrelated operations whilst in the middle of working in a protocol that somehow restricts what they can do. If they open a second copy of Neu3, though, the same protocol loads automatically (since it's linked to username).

We should add a commandline option "--no-protocol" to Neu3 that will start Neu3 with the protocol system disabled: any current protocol is not loaded, and the whole protocol window is not displayed, so no new protocol can be started (which would interfere with the previously running protocol, as we only track one started protocol per user).

Priority: not too high. Useful for a couple advanced users only.