Add operators 'has' & 'has-not', and shorten operators-word regex

[LemmusLemmus]

Aside from adding the two missing operators, I think the regex looks slightly better now by using extra groups to avoid repeating e.g. not-?

Sidnote

• It might be better to automatically generate the list of binary operators, using the output of help operators | select operator, but meh.
• Another currently not highlighted operator is the (unary) optional operator that can only be used on cell-paths. I might see if I can add it, but that will probably require improved syntax highlighting of various valid cell-paths.

[fdncred]

Thanks