add option to disable $where clause

[shanejonas]

Is your feature request related to a problem? Please describe.
I'm trying to use mingo to allow querying a just subset of data via an API, but i'd like to not allow $where or any eval clauses.

Describe the solution you'd like
As a user of mingo, for security purposes, I'd like to not allow any evals in queries such as $where: "this.foo && this.bar", is theres a way to disable it?

Additional context
Heres the reference on how to disable this in the mongodb documentation:

source: https://docs.mongodb.com/manual/reference/operator/query/where/#javascript-enablement

[kofrasa]

This seems reasonable. I will see if I can add it to the next release

[kofrasa]

In the next release $where will not be registered by default and must be included explicitly by users.

[kofrasa]

Fixed in 4.0.0