also made it more secure against copy'n'paste

This adds a custom event to the 'dokuwiki' template that allows plugin
authors to easily integrate custom pagetool buttons into the template.

This reverts commit 37764cbb.

This fixes the image display in IE7 with the disadvantage that now in
IE7 with images disabled the text won't be displayed anymore.

This makes the pagetools in non-hover/static/active-mode use another
image replacement technique that falls back to the text when images are
disabled. Furthermore this fixes the :focused-display in IE7 by using
:active, too.

For some reason without position: relative the search button is hidden
in rtl languages.

force screen_mode to string type (IE returns a number which is always triggering the default option in the following switch/case block

We removed them because of FS#2447 a while ago. But as the original
problem was most probably only caused by the gradient for the page
background and that's using a PNG now, the gradients for the buttons
should be fine. Please test to double check if this change causes
performance problems in Firefox.