bootstrap GsDevKit directly into extent0.dbf - 3.4.x and beyond

[dalehenrich]

As of 3.4.0 FileTree/Cypress read support is included in the extent0.dbf, so it should be possible to load GsDevKit/GLASS directly from git repositories.

The bootstrapGsDevKit scriptwas added back in October with commit df9cf851bea0898cb912392f31490e7ca9fd7d0f. Currently the script loads [Sport, Grease and GsDevKit[(https://github.com/GsDevKit/GsDevKit_home/blob/39defa2ef15f8151183d871e284368b5c3f94dbe/bin/bootstrapGsDevKit#L210-L224) as SystemUser.

Note that the load is done using GsDevKit project which is the parent project for [GLASS1}(https://github.com/glassdb/glass). The packages are identical between the two projects and they differ only by the fact that a different baseline is being used. Similar work will be done to convert the GsDevKit/Grease project to use SeasideSt/Grease and Metacello/metacello to replace the use of dalehenrich/metacello-work.

In addition to bootstrapping into extent0.dbf the upgradeStone script will be updated to use an upgradeGsDevKitImage instead of the old upgradeSeasideImage script ... this should result in the elimination of most (if not all) instance migrations that are currently incurred by the old scripts.