ENH: Replace Boost with ITK multithreading

no fibers found

all fiber sizes 8

changed num threads to 2, commented out some boost and is_branching

Works! identical to boost version

works without TractographyThread

tested with branching (10-30deg), works

itk determines number of threads

revert fiber.cc to original

get rid of boost references in tractography.cc

getting rid of old thread stuff

get rid of boost timer

Rip boost out of cmakelists, delete config.h.in

rip boost out of s4ext and superbuild cmakelists
update sample_run.sh and add its test data
FIX: Set multithreader's number of threads (important if user sets this)