And-based Multi Selection Added

* 3 options are supported for multi selection: “Single”, “MultipleAnd”,
“MultipleOr”, under “selectType” config property per facet.

* Default multi-select mode is based on whether facet attributes return
single values (“Single”), or multiple values (“MultipleAnd”).

* You can hold a modifier key to change the setting easily at runtime
(to “MultipleOr”, or to “Single” ). When holding a modifier key, mouse
cursor also changes to reflect the behavior update.