(maint) Share common acceptance setup

There are several (three now with SetParser) setup steps which are the
same between git and package acceptance runs.  This commit shifts them
to a common dir and uses symlinks to reduce duplication.
(maint) Ensure rgen gem installed for future parser tests

Acceptance hosts need rgen gem installed if we are testing with future
parser.  Also json for binder, though this should be deprecated soon.
Merge pull request #2154 from jpartlow/maint/master/common-acceptance-setup

Maint/master/common acceptance setup