All non-script changes from scripting branch

The major changes are

• [Breaking] No two components in a constraint system can have the same name.
• [Breaking] The value of a HotDrink variable is updated at once, and does not need to wait for the current promise to be settled.
• Allow variable references to accept null value.
  • Clarification: Only the flow types has been changed.
  • This might not be that breaking after all.
• Add simpler editing of components and variables with the edit method.
  • For example cs.edit.comp.var would return value of the hotdrink variable var in component comp for the constraint system found in the cs variable.
  • For example cs.edit.comp.var = 123 would set the value of the hotdrink variable var to 123 in the component comp for the constraint system found in the cs variable.
  • Nested components are not supported
  • Use the suffix _self to get either component or the variable reference.
    • cs.edit.comp_self would get you the component
    • cs.edit.comp.var_self would get you the variable reference
  • Editing is most useful when debugging a constraint system, e.g., in the console of a web browser
• Allow Subscriptions to have additionalSubscriptions
  • This makes it possible to attach multiple Subscriptions to the main Subscription to simultaneously unsubscribe from.
• Add variableListener and retainingVariableListener to simplify listening to changes in variables.
  • Note that it will not listen to changes in variable references.
• Add generic binders for HTML specific view: bidirectionalElementListener and elementAttributeBinder
• Allow ConstraintSystem, Component, Constraint, Method, VariableReference, and Variable to be serialized.
  • ConstraintSystem to json can be done with constraintSystemToJson(system)
  • json to cs can be done with constraintSystemFromJson(json)

And some minor changes

• Generally improve the types.
• Flow linting now throws errors instead of a warning, see .flowconfig for the active linting rules.
• Add back missing init make step required for the first installation.
• Fix the whap tutorial.
• Update all dependencies to their latest version.
• All files are now //@flow strict which means linting is stricter.
• All == have been replaced with ===.
• Lower delay in tests to make them run quicker.
• owner and system in Component can no longer be undefined, but still null.
• Expose owner getter in Component.
• Change the fresh names generators to not use # but rather _ to make automated names work with editing.
• Add hasVariableReferenceName to Component.
• Add componentByName to ConstraintSystem.
• Add allComponents to ConstraintSystem.
• Expose optional getter in Constraint.
• Expose owner and owningReference getters in VariableReference.
• Add qualifiedName function to VariableReference.
• Disable logging when testing.
• Add pExactStrings and pTryUnnamed to parsing.
• Throw exception instead of asserting resolving constraint system graph. This makes it possible to undo whatever made the system fail in a try-catch block.