Fixed HTML5 validator errors
Fixed HTML5 validator errors

- Generated code is now fully compliant
- Fixed DIVs
- Fixed CSS
- Fixed attributes of <input> (functions.php)
Merge remote-tracking branch 'origin/fraenzi-branch' into simon-branch
Added e-mail order confirmation
Fixed formatting problem in developer guide
Fixed Developer Guide markdown (special char?)

It seems that some kind of special character sneaked in. This is
the reason the markdown did not display properly. Re-added the
line and now it should work properly (!?)
modified css for button beautification
added some div's for button beautification
called function in checkout process to clear shoppingcart at the end