Analytics Component - tagged filters exclusion support

There is a really nice component for gaining advanced statistics, but it doesn`t support tagged filters exclusion. This would be very nice feature, since we use it for gaining data for price histogram, which should be independent on filters selected by user (of our eshop).
The Analytics Component was added in SOLR-5302.

I tried to add this feature in simplified way, where the tags are specified in param value turning
this component on, i.e. olap={!ex=tag_name}true.

Changes were inspired by SOLR-3177 and patch created is based on branch_5_4.