when launched from Finder, the PWD needs to be set

    - index.html → document.html
    - gui.html → index.html

Redrawing the crop marks with less, as the 4 values for
background-position does not seem to work in Arora.

Added example cases:
- 2 columns layout
- offset pagination
- 1 layout per page
- master pages

Put the 2columns example in an "examples" folder so that the boilerplate
stays as basic as possible.
Nota: you can use the class "recipient" to create a new box to flow
into.

Put the first launch before other operation to try to ease the learning curve, and some minor corrections

adding items to the README, discussing with Steph about moving most 'advanced' items out of the main README over to a 'dev' type file'

It is made using `-webkit-transform` because using the browser zooming
feature makes the rendering engine recalculate the layout, ending in
slight differences in word wraps.

In the "setup" folder, you can now edit local settings such as page
number, source of the content (which can be a remote URL like the export
URL of an Etherpad), page geometry…