CODEMGR_WS variable could be dynamic

[sac]

In the developer guide under section Setting the path to our workspace we explain setting
the CODEMGR_WS variable as: export CODEMGR_WS="/ws/rm/$GATE"

This could be made more dynamic by setting variable like:

export CODEMGR_WS="git rev-parse --show-toplevel"

@rmustacc Does this make sense? If so, I'll send a patch updating this.

[rmustacc]

@sac This is coming from the example environment files. It looks like the stock config file has been changed to match that which is different from when I had written this. Probably reasonable to update that.

[sac]

Ack!

[rmustacc]

I realized that might not have been clear, so please, feel free to send a patch.