Feature: Adding a LIKE operator

[david-alm]

Addresses concern in #85.
This adds an explicit LIKE operator. The idea it to enable developers to implement wildcard-based searches (such as prefix/suffix match).

[rafalp]

Hi! Are you able to provide a test case for this?

[tomchristie]

I'd really want a compare-and-contrast with the Django ORM before accepting something like this. They don't have a like filter, which is a strong indicator that there's probably some different tack for us to be taking here.

I'm still up for conversation about what differences we might have from Django in this regard , and if #85 needs any work as a result, but we'd need a clear resolution to that discussion first before accepting code changes.