Replaced osm point cache and RevTreeBuilder2's NodeIndex with mapped file implementations.

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.

The current RevTreeBuilder2 NodeIndex lead to high memory usage and could also be improved.
It is now replaced by MappedNodeIndex which is a NodeIndex backed by a memory mapped file
producing very little memory overhead compared to FileNodeIndex and approx. twice as fast.

Other implementations have been attempted, specially based on the mapdb libaray (see mapdb.org)
and are left for reference and future testing, but for now the two selected ones are the ones
mentioned above.