Add --clipboard-mode option

[Sryther]

Add the possibility to avoid using clipboard copy.

[ProMix0]

Does it interfere with clipboard-only option? Maybe more general approach with kinda clipboard modes should be used?

[Sryther]

Thanks for you feedback. I changed the way clipboard options are supported to have only one: --clipboard-mode which accepts always (default), no and only.

[Gustash]

Don't worry about which should take precedence over which. It's the user's fault if they provide both flags, they don't make sense together in the first place