Revised the time management in sim_core::run_sim(); not complete

Task @T11 : Time cycle management is now locked to the wall clock.
An exception will be thrown if the execution portion of the time
cycle exceeds a quanta's worth of micro-ticks. The quantas will
advance in steps of one quanta's worth of ticks, calculated
independently of actual elapsed time. This should provent slippage
unless a calculation cycle takes more than quanta * 2 ticks. This
should be detected by the exection timer, so we're good... Right?

Remaining tasks include collision resolution and output reporting.