Sample registration (rebase)

Also adds support for unit8 to the tiling api

Adds rest-hooks prototype (closes #87 (closed))

Staff feedback:

• Polyfill for debian 8 (h5web)
• Show zoom level?
• Loading indicator
• Mouse wheel zoom scaling (can be slow)
• Add correction to positions
• Export to image loading status
• Use generic selection logic (!500 (merged))