reflect models from discovery service

The idea is, calls to the following routes should return json data that's parseable into the brower using sails-backbone. There are three problems tho with the PR that @tjwebb should look at.

https://shackbarth-470-dev.localhost/demo_dev/backbone-models
https://shackbarth-470-dev.localhost/demo_dev/backbone-models/Honorific

Problems are:
(1.) https://github.com/tjwebb/google-discovery-backbone/issues/1
(2.) I'm seeing this error the second + time the route is accessed: 
```
Possibly unhandled AdapterError: Connection is already registered
    at Object.module.exports.adapter.registerConnection (/home/shackbarth/git/xtuple/node_modules/google-discovery-backbone/node_modules/sails-memory/lib/adapter.js:39:60)
    at /home/shackbarth/git/xtuple/node_modules/google-discovery-backbone/node_modules/waterline/lib/waterline.js:202:29
    at /home/shackbarth/git/xtuple/node_modules/google-discovery-backbone/node_modules/waterline/node_modules/async/lib/async.js:125:13
    at Array.forEach (native)
    at _each (/home/shackbarth/git/xtuple/node_modules/google-discovery-backbone/node_modules/waterline/node_modules/async/lib/async.js:46:24)
    at Object.async.each (/home/shackbarth/git/xtuple/node_modules/google-discovery-backbone/node_modules/waterline/node_modules/async/lib/async.js:124:9)
    at Array.async.auto.registerConnections (/home/shackbarth/git/xtuple/node_modules/google-discovery-backbone/node_modules/waterline/lib/waterline.js:175:13)
    at /home/shackbarth/git/xtuple/node_modules/google-discovery-backbone/node_modules/waterline/node_modules/async/lib/async.js:487:38
    at Array.forEach (native)
    at _each (/home/shackbarth/git/xtuple/node_modules/google-discovery-backbone/node_modules/waterline/node_modules/async/lib/async.js:46:24)
```
(3.) The discovery code is returning some data here:
https://github.com/shackbarth/xtuple/compare/xtuple:react...shackbarth:model-route?expand=1#diff-4279a638fd8b791f7a689932f2bd4cecR23
but it's not being transformed correctly.
```
{
  "models": [],
  "version": "0.0.0"
}
```
@bendiy FYI what I'm doing here is moving the guts of `getRest` into `getRestEngine`, which is a function that returns to a callback instead of writing to `res`. `getRest` calls `getRestEngine`, and writes it to `res`. But now the backbone model generator can also call `getRestEngine` and have it do something else.

That said, it's not that much code and the use cases are a bit different. Before this gets merged in it's possible that the code in `backbone-models` will just become an edited copy/paste.