[geometry][index]: error fixed in iterative spatial query visitor - because of the error, the first return value in the query performed for a tree with only one node (root==leaf) was omitted. iterative distance query visitor modified for consistency.
[geometry][extensions]: Added required includes to nsphere.hpp, missing if rtree.hpp wasn't included.
[geometry][index]: errors fixed in additional rtree utilities.
[geometry][index]: removed non-c++03 header from statistics additional utility
Move some template parameters from class level to function level in assign_value.