Java API Wrapper for the Skycoin node

## Expected Behavior

Access to the Skycoin node REST API implemented in Java code or as .jar assembly

## Actual Behavior

Right now this is only possible using code generated by SWIG , which requires memory handles

## Specifications

- Version: 0.25.1
- Platform: all
- Subsystem: all exported API sets

## Possible Solution

Generate with Swagger (share more info, please) . Beware of CSRF .

- [x] Use Skycoin node Swagger spec to generate initial Java REST API client
- [x] Add make target to automate generation in ./build
- [x] Aforementioned target should copy / merge relevant files into source code tree
- [x] README explaining the process
- [x] Mention in CHANGELOG
- [x] Patch the result Swagger-gen REST client to support specifying node address
- [x] Update package metadata
- [x] Run basic Swagger tests in Travis
- [x] Unify testing code if multiple frameworks are used across source tree
- [x] Beware of CSRF auth