Minor cleanups: remove unused variable + align "guide cover" reference element with the other reference elements.
Removed line breaks since these were not HTML line breaks (how to insert line breaks in the generated HTML?)
Implemented EPUB2 generation with
[async](https://github.com/caolan/async): creation of e.g. content.opf
requires that Images and Fonts dirs have been fully created.

Also
* Added a font and an image to IT.
 * Clean up of "project" directories and sub directories "Images" will be
 * implemented with:
  * Clean up of "user" directories and sub directories "Fonts" should be
  * implemented in a User.delete, if one such will be implemented in the
  * future.
  * Created private helper function, isSystemType.