Revert "Clean up EuiSearchBar docs and reorganize code. (#454)"

[cjcenizal]

This partially reverts commit 3a910d3, by moving the Query and Ast services back into the components directory.

Things I'm preserving:

• Change random.oneOf to accept an array.
• Import components into examples via the root components module.
• Refactor search bar docs for clearer data flow and render methods.
• Fix typos in docs.
• Import Enzyme utilities from enzyme root module in tests.
• Export Query and Ast services.
• Use Component instead of React.Component.
• Rename astToES to astToEs

[cjcenizal]

@uboness Can you take a quick look at this and let me know if this unblocks you?

[cjcenizal]

I'm going to merge this to unblock another PR. Let me know if there's anything else that's blocking you @uboness.