First of 3 modifier options working

Second of modifier use cases works

Updated builder modifier to test using pass through

Allowing pass through of arguments to self modifiers

New modifier tests work with subgraphs

Moved Graph._addModifier to use shared getNodeInfoFromModifier method

Moved Builder._addModifier to use shared getNodeInfoFromModifier function

Finished initial testing on modifiers

All tests besides silent deps pass

s/asyncBuilder/shepherd/