Got rid of one useless level in subdirectories. The approriate change has been done in star-offline-hft submodule
Updated pointer to the following submodules:

star-bfchain
star-ist
star-pxl
star-ssd
star-stevent
star-sti
star-offline-hft
Added new submodule star-sim
Made submodules to track their respective hft-dev branch