Make getParametersFromController public

`getParametersFromController` is currently private in `UniversalScheme`. It would be useful to client apps (like arc.js) if this could be made public.

1. it would be a little more reliable than using 'updateParameters' for identifying a scheme as being universal
2. it would make it easier to obtain the scheme's parameters hash, given an avatar

Find the UniversalScheme implementation and inspect the current visibility of getParametersFromController, along with how updateParameters identifies universal schemes. Make the method callable by client applications such as arc.js and verify that an avatar can be used to obtain the scheme's parameters hash.

Written by the indexing model from the issue text.