Sets a system variable.
getVar(key, onUpdate, onCreate)
Returns system variable value immediately.
onUpdate is called immediately, and on each update of the variable, with variable value.
onCreate is called immediately with a change listener reference.
Removes a system variable and its listeners.
Registers a system variable as persistent. Persistent variables are automatically saved locally when changed.
If variable was not saved locally earlier,
defaultValue is assigned.
resolveVar(variableString, onResolve, onCreate)
variableString is not a valid variable notation -
onResolve is called with
variableString is a valid variable notation -
onResolve acts as
onCreate then also acts as