Additions of:
-Skimming funcationality to fixed demand model
-Fixes to allow activity location on non-existent dirs (i.e. opposite sides of one-way links) to load onto the other direction (left-turn out of activity location)
-Updates to skimmer to save memory for large projects
-Error handling
Addition of basic background image tile loading capability and some changes to the scenario specification for skimming allowing for flexible update intervals