Adds a more restrictive filter for walking the VizNode tree
Adds a more restrictive filter for walking the VizNode tree

specifically, one that only returns nodes that are bidirectionally
connected. Also uses this new filter to determine which nodes are pulled
into the foreground.

pickettd/code-dot-org,rvarshney/code-dot-org,rvarshney/code-dot-org,dillia23/code-dot-org,dillia23/code-dot-org,rvarshney/code-dot-org,rvarshney/code-dot-org,dillia23/code-dot-org,dillia23/code-dot-org,rvarshney/code-dot-org,pickettd/code-dot-org,dillia23/code-dot-org,pickettd/code-dot-org,dillia23/code-dot-org,pickettd/code-dot-org,rvarshney/code-dot-org,rvarshney/code-dot-org,pickettd/code-dot-org,dillia23/code-dot-org,pickettd/code-dot-org,pickettd/code-dot-org,pickettd/code-dot-org,dillia23/code-dot-org,rvarshney/code-dot-org