Create "EM Atlas" plugin

[stephenplaza]

This plugin will be for viewing special locations manually annotated by the biologist. The key features are a search box to display and filter saved annotations and the ability to add new annotations in the neuroglancer react component.

The annotations will be saved in clio top level with an endpoint similar to "annotations" endpoint but with the ability to fetch annotations across all datasets. Prototyping can probably begin before the endpoint is available.

Features:

• search panel that gives a paginated view of all the annotations downloaded from the endpoint (show title, description, dataset, and thumbnail centered at the point)
• filter box on the top that will allow keyword search (each annotation will have a dataset name, title, description field, and timestamp). By default the newest entries should be on the top. There will only be hundreds of entries so it makes sense to have this all paginated in memory.
• the user should be able to click on an item and have that dataset and location loaded
• authorized users should be able to add a special "atlas" annotation to NG, providing a title and description. The interface will be very similar to the current 'annotations'