Add Like and NotLike condition builders

[mccolljr]

There's currently another PR with similar purpose open, but in my opinion it adds a lot of complexity that is unnecessary for such a lightweight feature. I have added Like and NotLike methods to the top-level namespace, both of which accept an optional ESCAPE parameter. In case you're skeptical (I was, as I had not used this before and assumed it went at the end of a condition), Postgres, MySQL, and Microsoft SQL all support the ESCAPE keyword, and it can be used inside a condition such as the following:

# matches movies whose name starts with '50%' and were released after 2000
SELECT * FROM `movies` WHERE `title` LIKE "50#%%" ESCAPE "#" and `release_year` > 2000 

(view on sqlfiddle: http://sqlfiddle.com/#!9/74b26e/1/0)

[taylorchu]

lgtm