ResourceBuff improvements and better error handling.

* added overloaded PopQty with eps arg to ResourceBuff

* ResourceBuff re-zeros qty_ member if all resources have been popped - to
  better deal with floating point issues.

* better error messages for ResourceBuff exceptions

* try-catch around RunSim to avoid core dumps when exceptions are thrown
Merge branch 'rwcarlsen-buff' into develop
nightly build