Add download widget

[jmcglone]

As a user, I should be able to download a local copy of the EPUB file I am reading. If a PDF file is also present, I should be able to choose to download either a PDF or EPUB.

• if an EPUB file is available for download, the download icon appears in the menu
• when a user clicks on the download icon and only an EPUB is available, an EPUB file downloads to the users desktop.
• when a user clicks on the download icon and an EPUB and PDF are available, a modal dialog is displayed allowing the user to choose either EPUB, PDF (or both?) to download.
• file size information is provided in the EPUB/PDF modal dialog
• uses open iconic font data-transfer-download via <span class="oi" data-glyph="data-transfer-download"></span>

This ticket requires the following items first:

• mockups of modal dialog and user flows

[jmcglone]

When a user clicks the download icon, a full-screen modal with check boxes to select available file formats is presented. By using check boxes, this implies it is possible to download both file formats
in a single step (downloading as a zip archive). If that is not possible, we'll need to change to a drop down/select or radio buttons.

NOTE: This only conceives downloading of an entire book, not book chapters.

[jmcglone]

@respinos mockup provided!