Revise parameter handling for snippets (ErikWittern#86)

* Revise example swagger to match test

There are three test cases dealing with array value query parameters
in test/parameter_example_swagger.json. The assertion for each of
these is wrong as it assumes the array should not be exploded.

However, two of these parameters are explicitly form style. The third
is implicitly form style because that is the default for query parameters.
None of them specify a value for explode, so this defaults to true.
Therefore the assertions are wrong.

See https://spec.openapis.org/oas/v3.0.3#fixed-fields-9

This commit does not fix the logic in the code, rather (for now) it
just updates the spec that is being used for the test to set explode
equal to false.

* create function createHarParameterObjects

This function takes an OpenAPI parameter and a sample value and
creates a HAR "parameter" object which is just a {name: "", value: ""}
object.

The function handles all of the variatons outlined in the spec
and this commit adds all the test cases that are presented
here: https://swagger.io/docs/specification/serialization

This function will be used in future commits to handle every
type of parrameter while generating snippets.

* refactor getParameterValues in terms of createHarParameterObjects

This doesn't change the functionality yet. This is just in preparation
for providing full support for all variations of parameters.

This commit breaks no tests but prepares us for more test cases.

* Add support for exploded values in query parameters

* Add support for simple style exploded values in path

* Add tests to demonstrate working label style path params

* Add tests to demonstrate working matrix style path params

* Add support for pipe and space delimited path params

* Add tests to demonstrate working object and array values in headers

* Re-order checks for candidate example param values

Per the swagger guide: https://swagger.io/docs/specification/describing-parameters/

"Using default to specify a sample value. This is not intended use of
default and can lead to unexpected behavior in some Swagger tools.
Use the example or examples keyword for this purpose instead."

Per this I think `default` should be the sample value of last resort
instead favoring `example` and `examples` first.

* Add support for samples in examples key

This works for header, path, and query parameter which
will now be discovered if the sample is in the examles key.

The snippet will choose the first example in examples.

* refactor getQueryStrings in terms of reusable method

getQueryStrings was doing something special that getFullPath
and getHeadersArray are not doing: considering both path
and operation level defined parameters. By parameterizing this
method on `in` we can later use it for `path`, `header` and
`cookie` parameters as well.

* Refactor getFullPath and getHeadersArray

These functions are now written in terms of
getParameterCollectionIn which does the following correctly

* Considers path and operation parameters and overrides
  appropriately
* Resolves parameter references
* Resolves schema references
* Looks at example, examples, schema.example and default keys
  looking for sample value

So now getFullPath and getHeadersArray benefit from all of this
logic. Each had one or more short comings.

* Add support for cookie parameters

* Resolve examples objects as needed

Author: michaelgwelch