Add --no-colour command-line option

[kristopherjohnson]

Adds a --no-colour command-line option that will disable colourised output even if the output device/stream supports it.

[rcdailey]

You misspelled "color" :)

Probably best to use "color", for example Git uses this spelling. Next person to add a color-based option might be American and use a different spelling. It will cause confusion.

[nabijaczleweli]

It's "colour", you filthy colonial!

But "color" is a better option here, because everyone uses it now. audible sigh

[philsquared]

Apologies for the premature closure - I deleted the branch and it auto-closed all associated PRs - it wasn't intentional.
I also can't re-open it at this point - but I'll come back and review shortly.

[lilith]

This flag would be extremely useful, as without it Catch and CLion do not get along well at all...