COMP: Add cmake option to enable OpenMP
COMP: Build sim interface and programs by default
ENH: Generation of non-abutting extent partitions

Added option to the ExtentPartitioner such that
it can generate abutting and non-abutting partitions.
By default partitions will be abutting, unless,
SetAbutting( false ) is called on the partitioner object.
BUGFIX: Fix interval split

Interval split was always assuming that the extent is starting
from 0. Also, restructured some of the code to simplify it and
make it easier to read.
ENH: Add method to compute extent intersection
ENH: Stream & density field openmp parallelization

This commit adds basic threading of the multi-stream and
density field calculation using openmp.