simple DRC: check for multiple drivers
fix source of PortTypeValues used for comparison
fix position of comments in test case
exception-throwing nits
Merge pull request #128 from mtrberzi/issue118-netlist-construction

Netlist construction from schematic
Merge branch 'master' into issue119-simple-drc

Conflicts:
	src/main/java/org/manifold/compiler/back/digital/Netlist.java
fix null pointer bug on certain test runs
Merge remote-tracking branch 'public/master' into issue120-vhdl-codegen
Merge branch 'issue119-simple-drc' into issue120-vhdl-codegen
log4j downgrade to 1.2
add simple test case for output product