App state is not correctly cleared between sample loads

[krokicki]

When you load a Sample or Workspace into Horta, it caches information in different objects through-out the app. If you open a new sample, sometimes the neurons are loaded in the wrong coordinate space, or there may be other issues. Many of these issues come down to clearing out the state through-out the application.
We need to ensure that every setting and state is reset before a new Sample or Workspace is loaded.