Path separator in coin instructions

It's a pain to re-write coin instructions for windows and non-windows OSes. It also doubles the configuration size and complicates the logic. I see two alternatives to improve the situation:

IMO the best solution would be to

• Make Coin interpret the forward slash / as the universal path separator. Internally it would translate it to backslash when needed on Windows.

Alternatively, much easier is to

• Introduce an internal variable Slash that can easily be expanded in a cross-platform way, for example:

  variableValue: " {{.SourceDir}}{{.Slash}}coin_qnx_qemu_runner.sh"