Downcase attribute and query for case-insensitive search

[dwightwatson]

A minor change to the collection engine that allows case-insensitive search by simply downcasing the attribute and query arguments before calling contains. Using the test data at the moment a search for a lowercase otwell wouldn't match either of you because your names are capitalised.

[driesvints]

This isn't always wanted I think. A real-life situation of a search engine involves case sensitivity. For example: https://www.algolia.com/doc/guides/managing-results/refine-results/faceting/#case-sensitivity

We could indeed make an exception for the collection engine since it's more meant as a testing playground.