Refactored type definitions (#1119)

* Updated types generation script

* Refactored api method definitions

* Updated test
- Removed old test code
- Added tsd dev dependency
- Rewritten test with tsd

* Removed unused dependencies

* Fixed definition

* Updated test

* Updated docs

* Improved events type definitions

* Updated test

* Minor fixes in the type definitons

* More type test

* Improved Transport type definitions

* Updated test

* Addressed comments

* Code generation

* Use RequestBody, Response and Context everywhere, also default Context to unknown

* Updated test

* body -> hasBody

* Fixed conflicts

* Updated code generation

* Improved request body type definition

* Updated code generation

* Use BodyType for both request and reponses generics
- Use extends for defining the RequestBody generic to force the user
  following the same shape.
- BodyType and NDBodyType now accepts a generics to allow injecting
  more specific types in the future

* API generation

* Updated test

* Updated docs

* Use BodyType also in ReponseError

* Removed useless client generics

* Renamed generics and types
- prefixed all generics with a T
- BodyType => RequestBody
- NDBodyType => RequestNDBody
- Added ResponseBody

* Updated test

* Updated docs

* Test ResponseBody as well

* Simplify overloads

* API generation

* Updated test

* Updated error types

scripts/generate.js

@@ -58,7 +58,7 @@ function start (opts) {
       { encoding: 'utf8' }
     )
 
-    const { fn: factory, types } = genFactory(apiOutputFolder)
+    const { fn: factory, types } = genFactory(apiOutputFolder, [apiFolder, xPackFolder])
     writeFileSync(
       mainOutputFile,
       factory,