Describe the bug
Panel position is being reset to what is specified in the global options.

To Reproduce
Steps to reproduce the behavior:

1. Run CRA example (note: panelPosition: 'right' is set in the options)
2. Open /?path=/story/button--with-text
3. Switch addons panel to the bottom mode
4. Open /?path=/story/button--with-some-emoji
5. Addons panel position is reset to the right mode

Expected behavior
Addons panel should be still displayed in the bottom.

Code snippets
Looks like the problem is here:

// lib/ui/src/core/context.js
api.on(STORY_CHANGED, id => {
  const options = api.getParameters(id, 'options');

  api.setOptions(options);
});

// lib/ui/src/core/layout.js
const updatedLayout = {
  ...layout,
  ...pick(options, Object.keys(layout)),
  ...checkDeprecatedLayoutOptions(options),
};

setOptions is being called after every story change, and panelPosition is being reset to what is specified in the options, as ...pick(options, Object.keys(layout)), overrides whatever is in layout.

System:

• OS: MacOS
• Device: Macbook Pro 2015
• Browser: chrome
• Framework: react
• Version: 5.1.0-alpha.6