display errors from nodenetrunner in frontend

also, make exception alert scrollable for tracebacks
"reload native modules" now also reloads nodetypes

plus, display the full error with stacktrace to the user if something goes wrong during reloading.
add worldrunner exception tracking

also, store exceptions by uid.
add a changelog
better error reporting if server offline
performance tweaking for nodenet stepping
get rid of redundant keys() calls
more redundant .keys() calls
convert sheaf elements to dict
pause runners if no active worlds/nodenets
slight optimization of slot/gate fields
fix reload nodefunctions
update monitor list, if slot monitor added

(also, fix refresh on monitor removal)
remove some dict.get methods
remove unused nodespace parameter
allow worlds to inherit from one another
Update README.md
Implementing client to server chat messages that
will allow us to teleport.
Merge branch 'master' of github.com:joschabach/micropsi2
rename sheafElement to emptySheafElement