Make the syntax somewhat more forgiving

[snej]

1. It would be nice if the tokens property were optional. Many of my rules don't use tokens, so I forget to add them, but currently it's a fatal error if a lines block doesn't contain a tokens property.
2. It would be handy if there were some color synonyms, so I didn't have to remember the exact names. For example, "Gray" as a synonym for "LightBlack", or "Orange" for "Yellow".

[dalance]

At v0.4.3, tokens can be omitted. About 2, I can't judge which synonym should be added because color recognition is affected by difference among individuals. (For example, I recognize "Orange" and "Yellow" are different color)