Handle arrays of value in parameters

[aledt]

We should look at how we support arrays of values.

For example, in the in param, does it makes sense to accept a list of parameters which are parsed as individual values?

So would the query string of value=in:item_a,item_b,item_c provide a filter object of:

in_=['item_a,item_b,item_c']

or

in_=['item_a','item_b','item_c']

I think this actually goes a bit to the question of how we handle OR and AND values since normally, a list of items in an object like this would be ANDed together?