Android API wrapper for Skycoin node API

## Expected Behavior

Access to the Skycoin node REST API implemented in Android code or as an assembly.

## Actual Behavior

Right now this is not possible

## Specifications

- Version: 0.25.0
- 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 Android 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