N1QL array slices should include defaults for start and finish

The array slice operator takes a start and an end index, like this: [start:end]. In Go and other languages, these indexes are optional, with sensible defaults. You can include one, the other, both, or neither.

https://tour.golang.org/moretypes/10

Currently in N1QL we require both indexes to be provided. We should allow them to be omitted.

This would be a very good first project for someone new to the query engine. It is well defined, not too big, and introduces them to our parser, algebra representation, and expression code.