TagTranslator misses functionality to resolve OSHDBTagKey

[SlowMo24]

Problem Description

The TagTranslator provides a function to get from OSMTagKey or String to OSHDBTagKey but not the other way around

Expected Solution

Add lookupTagKey

Alternative Solutions

Make lookupTag return "all it knows" i.e. an OSMTag with a key but Null value. This would allow this function to serve the above information.