Modify line properties for documents without layers

[cfcurtis]

This has been a fairly common request, and relatively straightforward to implement (mainly UI trickiness). It's still not going to give great results in many cases as it will apply blanket line property modifications to all lines, but it seems to be behaving for cases where people just want to make lines a bit thicker (for example).

In doing this, a couple of small (and likely very old) things were changed:

• Swapped the order of CMYK and RGB, as the colours can look subtly different and RGB is more common (so coming second makes it take priority)
• If a "G/g" command is issued, the entire colourspace is set to greyscale and RGB mods are ignored. I'm now replacing all Gs with the selected line colour.