feature: add support for logical and filtering by taxonomy

[bendeca]

I had the task to implement a filter system accross multiple taxonomies. The current system only allowed for one taxonomy parameter in the request, taxonomies were separated by '|' and handled as logical or. https://example.com/!/Fetch/collection/xxx?&taxonomy=category1/foo|category2/bar This would return all collection with the logical condition: category1 == foo || category2 == bar

With multiple taxonomy parameters, only one was registered (the last one) https://example.com/!/Fetch/collection/xxx?&taxonomy=category/foo&taxonomy=category/bar This would return all collection with the logical condition: category2 == bar (the first taxonomy parameter is ignored when multiple parameters have the same name)

What I did was add the possibility to combine multiple taxonomy parameters to an array in the request: https://example.com/!/Fetch/collection/xxx?&taxonomy[]=category1/foo&taxonomy[]=category2/bar

Now the taxonomy parameter cought by the setParameters() function will contain an array and each taxonomy (or taxonomy group) in the array will be handled separatly.

so the above request would rerun all collections with the condition: category1 == foo && category2 == bar

these methods can be combined, so: https://example.com/!/Fetch/collection/xxx?&taxonomy[]=category1/foo|category3/fizz&taxonomy[]=category2/bar|category3/buzz would return collections with:

(category1 == foo || categroy3 == fizz) && (category2 == bar || categroy3 == buzz)

[aryehraber]

Hi @bendeca, thanks very much for the PR! I'll try and review this soon 👍