Add support for more datatypes in filters (e.g. keyword, quantity)

[krabina]

Semantic Drilldown displays an error when data type quantity or keyword is used:
Error! Unsupported property type (Quantity) for filter Size.
as quantities support multiple units, I guess using the first unit would be ok.

https://testwiki2.kdz.eu/index.php?title=Special:BrowseData/Cities

If a property is selected of datatype keyword, SD displays "(There are no values for this filter)" even if there should be values (same query is working in filtered format.
There is also an error message
Error! Unsupported property type (Keyword) for filter Numismatic keyword.