Allow manual collapse sidebar

.. but need to add a toolbar button for Mac since the
old show/hide button on the scope bar has been removed
since it is now in the wrong place.
Merge branch 'master' of github.com:GoldenCheetah/GoldenCheetah
UI Nits: Sidebar, invisible root item for intervals
Mac sidebar button image

.. as template image for NSButton
Mac Sidebar button in toolbar

Button to toggle sidebar, also changes as we manually close
the sidebar by dragging, similar to behaviour in XCode.
LTMPlot fix baseline setting

.. it was lost when fixing bar style drawing.
.. maybe we should also allow fill under curves?
Merge branch 'master' of github.com:/GoldenCheetah/GoldenCheetah
UI Nits: QSplitter cosmetics

.. prettified on a Mac.
.. still need to work on icons
Merge branch 'master' of git://github.com/GoldenCheetah/GoldenCheetah into upstream_master
Merge branch 'upstream_master'