Replaced osm point cache by a better implementation and improved RevTreeBuilder2's NodeIndex.

The current osm point cache performance declined severely as the number of coordinates
increse, since the temporary bdb je database competes with the staging and object db's
for heap memory on the shared bdbje cache.

It is now replaced by MappedPointCache which is a PointCache that uses a memory mapped
file to store the coordinates in sorted chunks, and hence doing most of the work in
off-heap memory, several times faster than the bdb je implementation. It also stores
ordinates as ints following OSM's to/from decimal conversion rules.

The current RevTreeBuilder2 NodeIndex lead to high memory usage and could also be improved.
It is now improved and its interface extracted to allow for alternate implementations.
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