Make Toast callable more than once

Now we queue messages. There is no transition between two toast messages yet, because
a fadeout/fadein effect would appear after the new text was set, which looks ugly.
Drop unused styles after removing the administration
Switch from a with display:block to a div which onclick

Otherwise the validation will warn because we have a div in an a-tag, which basically
is disallowed. One should not use block elements in inline elements.

See http://www.w3.org/TR/REC-html40/struct/global.html#block-inline for details
Implement a simple way to distinguish a development instance from a productive one