Setting additional options could be imported via strings

[markfinal]

Setting the additional options could be made easier if there are a lot of them.

For instance, perhaps you copy-n-paste from a Conan command line, e.g. -o A:x=y -o B:s=t.

Or, you may keep them in a YAML file, e.g.

A:x: y
B:s: t

Either way, an importing mechanism would make it easier than copy-n-pasting each one in return.