minor code reuse modification
Merge branch 'nodenet_sheaves' of github.com:joschabach/micropsi2 into nodenet_sheaves
Merge branch 'nodenet_sheaves' of github.com:joschabach/micropsi2 into nodenet_sheaves

Conflicts:
	micropsi_core/nodenet/node.py
Introducing cat/exp for pipes, sheafed cat-checks.
Doesn't work yet, I need UI to check this.