WIP: GoDaddy Contributions

Corrected generateModelDefinition() to scan for model references in remote accepts, returns, errors, and nested models
Changed addRoute() to honor X-Forwarded-Host
UI/UX cleanup for SwaggerUI
	Add support for toggling Model and Schema, instead of just expanding
	Added guard against null mockSignature
	Added support for toggling Model and Schema, and added support for primitives in StatusCodeView
	Changed to hide the message-bar when no message
	Changed to use defaultValue, if present, for sampleValue
	Changed to use relative path for images/throbber.gif for mounting into apps at different levels
	Collapse and label responseModel description by default
	Correct description of collections of object and nested
	Corrected to avoid showing invalid Model and Model Schema is missing or void
	Corrected to load images relative to swaggerRoot, for nested context root
	Corrected to work when loading resources from file://
	Ensure Response Content Type is shown regardless of Response Class
	Omit divs for info.title and info.description if they're absent
	Removed 'Implementation Notes' label since it's just noise, widened Resource expansion anchor to full label

**Tasks**
 - [x] https://github.com/strongloop/loopback-explorer/pull/58
 - [ ] `X-Forwarded-Host` header (#61)
 - [ ] `apiVersion` and `swaggerVersion` (#61)
 - [ ] UI customization (`contentWell`) (#61)
 - [ ] describe models for accepts and nested returns  (#61)
 - [ ] response and error messages  (#61)
 - [ ] additional param metadata like `pattern` and `enum` (#64)
 - [ ] upstream swagger-ui and swagger-js changes
@bajtos - We'll need to coordinate on the swagger-js and swagger-ui PRs, because you have style overrides and we have overrides, so we need to find a way for those to work together.  We need a way to easily have local colors and fonts, but we should be able to agree on layout and spacing.  If we can find a way to make the top-level and embedded cases both work and still have custom styling, I'm happy to strip out the styling changes from swagger-ui and then submit the rest.

I believe swagger-js only has universal changes, but includes an extension to Swagger Spec for documenting multiple basePaths for multiple environments.  I'm not sure how they'll feel about the last, but am happy to keep it in my fork if necessary

The only functionality loss I see for sure is the Response Content Type not being shown for Response Messages, see: https://github.com/shelbys/swagger-ui/commit/16ad569af8a8379d7736b56052351bf32557a0d5  Everything else seems to be bug fixes and usability