* In a couple of places I had to resort to if(IsHighContrast) but mostly
this is just using system brushes consistently or not assuming black
text.
* The default DockPanel theme doesn't work well, so make a minimal high-
contrast theme for it and assign it everywhere.
* The pipeline flow was using fixed colours, use system brushes for the
different elements and switch based on high-contrast to ensure active
and inactive stages are visible (using ActiveCaption looks bad on
normal themes because it's a big block of colour).
* For some reason the flat toolstrip renderer doesn't handle white-on-
black themes, but the system one does. It's a little clunkier but it
shows up correctly without writing tons of custom painting code.
* Range histogram uses a properly contrasting colour for the border.
* Treelist views use a better system colour for selected rows when
inactive and hovered rows (when high contrast).
* Mesh view grids have a system background instead of white
* Various things (pipeline state, mesh viewe) set text colour when
colourising backgrounds of things instead of assuming black.
* This seems way more reliable and smaller than shipping a compiled .dll
* For some reason I didn't find this method before (I only knew that
you could ship the loose files which wasn't a good solution).
* Errors like syntax and runtime errors in python are thrown as
exceptions. So for when we invoke onto the renderer thread to do some
work, we need to be able to catch those exceptions otherwise the whole
program dies. So over the execute, temporarily switch the thread into
a catching-exception mode, which then gets rethrown on the invoker's
thread.
* Note that BeginInvoke shouldn't be used by python since the callback
might happen after the execution has finished (there's no way to wait
at the moment).