Enable filters & searchable fields for the array grid provider

[LBannenberg]

This PR does the following:

• Allows you to limit searchable fields for an array grid. If you specify them in layout xml then only those fields will be searched. If you don't set this, you still get the old behavior.
• Allows you to filter ArrayProvider based grids, using the 'like', 'equals' and 'from_to' condition types.

I've tested these in the module I'm building here: https://github.com/LBannenberg/magento2-composer-dashboard, although I had to twist the from_to a bit because I'm not using that directly.

I didn't have a clear example of the 'in' condition type being used, it seemed like you might want to use it for a multiselect situation (customer groups, stores)? Without a good example of it in action, I haven't implemented that, so you'd safely fall through to the default case (line 99).

[jissereitsma]

Very nice! I simple didn't get to this functionality yet. And I have to say that I didn't have a clear vision at the time how this could be best implemented, mostly because ArrayProviders lack features like performance-friendly pagination. But anyway, this PR is awesome! Thanks!