Convert GLASS1 to use SeasideSt/Grease and 3.6.0 port

[dalehenrich]

Contrary to popular belief, the GLASS1 baseline uses GsDevKit/Grease, not SeasideSt/Grease, despite that, it seems that the actual code loaded into GemStone is identical in both repositories, so it is a technical difference at the moment.

3.6.0 will require some changes in Grease (it looks like), so it seems to be a good time to make the switch.

The major impact is that GsDevKit_home will start cloning SeasideSt/Grease for new installations (GsDevKit/GsDevKit_home#295) and I will be looking into trying to automate the update for old installations ..

[dalehenrich]

decided not to switch Grease git reos, closing per GsDevKit/GsDevKit_home#295