Add rich text editing to about page and documents/resources page

[CodyGramlich]

Resolves issue #105.

Some of this work was started by @TheBroMoe.

• Added the ability to add multiple editable sections with a rich text editor (QuillJS)
• The edit page button only appears when the admin user is logged in
• Added a page object that looks like:

  export interface Page {
  title: string;
  documents: Document[];
  created: number;
  }

  and a Document object that looks like

  export interface Document {
  guid: string;
  content: string;
  }

• Added a custom handler to the upload image button on the text editor toolbar so that images get uploaded to imgur and then the link is returned in the response and inserted into the editor (by default the images were Base64 encoded)
• The html of each document is sanitized on the backend
• Replaced the about page component and quick-links component with a page component
• Changed font of the entire application from Open Sans: 600 to Open Sans to allow for <b> and <strong> tags to have an effect.
• Added a pages index to elasticsearch that stores Page objects that are referenced by title
• Added the pages and the page mappings to the upload service and backup service