Added support for user metadata array field and "contains" comparer

[olegrumiancev]

Hi there! First of all great plugin, and thank you for all the hard work on this.

I've had to edit metadata visibility test file in my instance to be able to compare custom user field that's a multiselect, resulting in array to a string value, essentially checking if an option was selected.

I figured this would be a nice easy addition to the plugin