Adds a new grape-based RESTful API to support "GET" ops on the node/model slices
(along with a corresponding grape-swagger-style documentation layer for the RESTful
API that we are adding)
Adds in a new grape-stype RESTful API for the boot/config/image slices
(and removes some extraneous code from the model/node slice APIs that
have already been added).  Also includes modifications to Razor to
support an additional configuration parameter that can be used to set
the web-service root context (websvc_root) and assigned it a reasonable
default value if it's undefined (/razor/api/vi).

Note; with these changes in place we can now boot a node into the
Razor Microkernel using our newly-defined grape-style RESTful API
added in tests for accessiblity of a few of the resources defined to date
(specifically, added tests for accessibility of the /config, /config/ipxe,
and /boot resources; the first two should only be accessible directly from
the Razor server and the last should only be accessible from the Razor
subnet