BUG: Ensure ErrorLog/PythonConsole menu entry bring dialog to foreground

This commit partly revert commit r19500 making sure the errorLog and
pythonconsole menu entry are non-checkable. It means that if one of the
dialog is already shown but in the background, selecting the menu entry
will bring the dialog to the foreground instead of hiding it.

Also simplify who the errorLog button interact with its associated
ErrorLog dialog by simply associated the corresponding QAction.

Note also that the QAction icon is the one that is now
highlighted/unhighlighted based on the addition of new
warning/error/cricial messages. The icon is now updated both
in the bottom right corner (Error log button) and in the menu entries.

See issue #1349

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22307 3bd1e089-480b-0410-8dfb-8563597acbee