Adds pattern matching syntax to without.
Adds pattern matching syntax for has_fields.

This also adds it for with_fields since that just rewrites to
has_fields.
Make other obj_or_seq functions not recurse on seq of seq.
Make pattern matching work with group_by.
Adds tests for without.
Adds tests for pattern matching group_by.
Adds tests for has_fields and with_fields.
Adds pattern matching in without docs.
Adds docs for pattern matching group_by.
Adds docs for pattern matching with_fields.
Adds docs for pattern matching has_fields.
Merge branch 'next' into merge_br

Conflicts:
	src/rdb_protocol/func.hpp
	src/rdb_protocol/terms/obj_or_seq.cc