Initial work on issue #112

* Fix Python libs makefile for cross compile
* Create Makefile.modelsim so now can run example using make SIM=modelsim
Major overhaul of Scheduler as per issue #121
Merge remote-tracking branch 'origin/Issue#112' into issue#121
Get modelsim working #112 on top of scheduler re-write #121
Issue #112: Correct Modelsim makefile to depend on libraries
Fix Python Makefile: 'site-packages' isn't always present in distutils.sysconfig.get_python_lib()
Account for incosistent arguments for $fatal vs. $info/$warning/$error
Updates to simulator makefiles for Aldec and Modelsim
Ensure we unprime all triggers when tearing down after a test
Ensure we advance after every schedule, otherwise we don't start the next test
Correct erroneous address
Tweak to scheduler and coroutines

* Fix for coroutines not marking themselves as complete
* Scheduler only advances on calls from the simulator
* Added note about possible problem with ReadOnly triggers