Don't use a leading dot in URLs

All of the changed URLs should be absolute resource paths.
Use absolute paths for tiles in session editor

The session editor is now at a RESTful location, so relative paths to
tiles won't work.
A sesssion's 'hideAnnotations' field should be a bool

The old code allowed it to be treated as an int in some cases, and past
commits didn't fully account for this.
Merge branch 'session_editor_fix'

* session_editor_fix:
  A sesssion's 'hideAnnotations' field should be a bool
  Use absolute paths for tiles in session editor
  Don't use a leading dot in URLs