Various improvements to search with special phrases for Python frontend

[lonvia]

• Change SQL to not return duplicates of places. This was restricting the number of actual results returned to something well below the stated limit.
• With near searches, order results by distance to the center of the place.
• Avoid duplication in the list of categories in case where different languages transliterate to the same word token.
• For near searches further restrict the list of places taken into account as being near to.
• Avoid qualifier searches when the special term makes up a complete phrase (e.g. "Hotel, Vaduz" is read as "search a hotel in Vaduz" while "Hotel Vaduz" is read as "search a hotel named Vaduz")