* Intended to preserver scroll-state (which is shifted when an element to the bottom gains height). However too unstable to be more handy that it is annoying when it is not.
* Follows-up r107982
* Previously mw.log and mw.Debug both were in a fixed container on the bottom, overlapping each other. mw.log did increase the body's padding-bottom to account for the height so that all content is still visible, but it was still a problem when mw.Debug came along.
* This plugin adds a single fixed position element to bottom of the body, to which other stuff like mw.log and mw.Debug can append a non-fixed position container. That will take care of it.
* Method update() will re-check the padding and scroll position and fix where needed
* Reduces code a little bit
