Move handling of LIKE patterns to the compiler.

LIKE patterns are an SQL-ism, so this converts them to regex _before_
the LogicalPlan rather than after.
Enable escape characters for LIKE patterns.

Fixes #65 and cleans up a few other hacks:

* got rid of the `NotIn` and `NotLike` Binops and std lib functions,
* change parsing of “suffixes”, and
* rename LogicalPlan’s `Like` to `Search`.