Refactoring of websocket package

[lorenzodonini]

Proposed changes

Refactors the package to improve code structure, abstracting away some functionality and also allow for new features to be added on top more easily.

Included changes:

• webSocket now includes most of the actual communication logic, including:
  • read/write pump
  • pingPong logic
  • connection configuration
• Server and Client logic was split into server.go and client.go
  • both rely on the same webSocket struct for actual communication, streamlining the channel logic and removing some duplicate code
  • renamed the top-level interfaces
• Added support for bi-directional PingPong (can be initiated on both client and server)

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

Checklist

• I have read the CONTRIBUTING doc
• I have signed the CLA
• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged and published in downstream modules