Add snippits to the data explorer

Feature:
- Be able to save and reuse my commonly used snippits of flux.
- be able to insert them into my query similarly to how flux functions and variables work.

@mavarius and I have done some work to start on this branch: `hackathon/snippits`

on this branch, we are storing snippits in local storage and it will appear anywhere time machine is used. It should probably be limited to the data explorer so you dont get a nested overlay situation.

Start by reviewing the existing work on the `hackathon/snippits` branch and how the data explorer uses local storage and time machine overlays. Done should mean users can save and reuse Flux snippets, insert them into queries like Flux functions and variables, and see the feature limited to the data explorer.

Written by the indexing model from the issue text.