Remove HTML5 Shiv javascript

html5shiv has been added to fix IE8 problems (see ARCHE-296). UNfortunately the LICENSE was not updated with html5shiv copyright statement.

I decided to delete the javascript file. This means the problem described in ARCHE-296 will re-appear in IE-8.
I think that acceptable because:

• for the outside world, archetypes has already been replaced by archetype (from essentials) even for 7.9,
• we will soon drop support for IE8