convert sheaf elements to dict
pause runners if no active worlds/nodenets
slight optimization of slot/gate fields
remove some dict.get methods
remove unused nodespace parameter
rename sheafElement to emptySheafElement
Merge pull request #44 from Doik/backend_performance

Doiks backend performance patches
adds activation setter for gates.
Merge branch 'master' of github.com:joschabach/micropsi2
Revert "Merge branch 'master' of github.com:joschabach/micropsi2"

This reverts commit 814a4b7e7d33634c71580ee666132ba3a60dc9a9, reversing
changes made to b3c3b98fedb4ec6bf292f59afa101ed272d9c39e.
Revert "adds activation setter for gates."

This reverts commit b3c3b98fedb4ec6bf292f59afa101ed272d9c39e.
adds activation setter to Gate.
merge with upstream master