Rewrite BIHTree.

* reimplemented BIHTree (same interface), using tru Bounding Interval
Hierarchy concept, thats every element is stored just once.
* make unit tests for the BIHTree that checks result against full search
* fix bug in field_interpolated, keeping old searched elements in the result
   vector
* add missing noncompatible_small.msh
* global_defs : ASSERT_LE macro