Make sure to use the classtype tables with near search and
allow to search for arbitrary key/values (forbidding it
for viewbox searches).
Add tests for near queries.
Reenable search by the secret special term [key=value]
matching against the given main tag. Note that for most
cases that works only for tags that also have a special
search table.
When searching for POIs in place_classtype_ tables limit the number
of objects considered to 300. The distinct and order by clauses
forced until now to retrive all matching objects and order them
first which can cause long running queries when retriving them
for large areas like the US.
Fixes#735.
