This removes the base z-indexes as they seem not to be needed (source
order defines initial heights) and interfered with the sidbar functionality.
Removing it was suggested in SPR-899 as well
There is no need to differentiate between site tools and the navigation
anymore. Instead now it's differentiated between the navigation tools
and the displayed content.
Now all toggling of the sidebar and the related menus is done through
the same click handler. HTML has been unified. All sidebar related
content is now in a single include file instead of several. Icons for
the site tools user tools and trace have been added.
The CSS for the whole sidebar still has to be refactored.
