Fixup sidebar cosmetics for Linux

.. embossed offset is 2 there too.
UI Nits: QSplitter colors on Linux

.. just adjusted to be more Gnome friendly.
UI Nits: Splitter icons adjust

The icons are adjusted via utility function iconFromPNG()
which currently just adjusts the icon color to be a muted
gray as opposed to black.

This is the first pass at recreating the 'template' function
used by the cocoa image functions. Will add an emboss feature
later, but at least now they are less vibrant and when clicked
turn black giving a visual clue that they are clickable.
UI Nits: Sidebar remember their state

Rather than relying on the parent to maintain the splitter sizes
and states, the GcSplitter remembers its own state and sizing.

This includes remembering if the children have been hidden via the
icon bar at the bottom of the splitter.
UI Nits: Stop unhiding the sidebar

.. when switching views. It seemed like a good idea at the
time, but now it is really irritating. If I want the sidebar to
be shown I'll select it thanks.
UI Nits: Images embossed

.. akin to the NSImage 'template' function we now pre-process
the GcSplitter icons to get a shaded and embossed look. Its a bit
clunky code, but its only run at startup.
UI Nits: Center Icon Bar
UI Nits: Emboss Splitter + - menu icons

.. changed icons since they don't emboss well algorithmically
(yeah, the algorithm is very basic for now).
Merge branch 'master' of git://github.com/GoldenCheetah/GoldenCheetah into upstream_master
Merge branch 'upstream_master'