Issue 1482 refactor

[frantuma]

As discussed with @fehguy, PR aims at fixing and references issues #1482 #1384, PR #1397.

It basically allows to configure more than one "Swagger context" (logical concept including SwaggerConfig, Swagger initial info and used Scanner instance) in same JVM and same web application, one for each configured servlet/servletConfig.

An example of "multi context" setup can be find in samples project PR swagger-api/swagger-samples#46
where a "swagger.context.id" initParam is provided for each separate "swagger context" instance (see sample web.xml)

Approach is sub-optimal, but as discussed quite some additional refactor would be needed to accomplish a nicer solution, with quite high risk related to compatibility.

[webron]

As @fehguy mentioned, I assume this doesn't solve #1103. I think it's fine if it solves the other issues, and the solution to #1103 will be a separate one (there's a pending PR which may solve it, I think).

[frantuma]

@webron it should actually possibly solve it, I just updated last remaining unchecked ref to context (kind of quick fix, ReaderConfig still only configurable via context), but tests and samples would need to be run/checked to confirm

[fehguy]

I've verified this works. There is a slight change in usage though--as shown in the samples, this:

context.setAttribute("swagger", swagger);

has been replaced with this:

new SwaggerContextService().withServletConfig(config).updateSwagger(swagger);

We'll update the release notes