add dev task to reload file tree (reloads prims as well)
add a task to reload everything, reloads smalltalk code, filetree, and
prims
change update.sh script to attempt in-place update, do a clobber and
full rebuild if that fails
exit earlier when a failure occurs during stone building
test update script's in-place upgrade by running vmunit tests twice with
an in-place update in-between