Create Session Extraction engines

Essentially they are classes that implement
the thenable interface.
Integrate Engines with Session and cleanup code
Add timeout for XDomain session extraction
Refactor Session
Update API to support after load usage

Replace API endpoint (window.sa) on payload load.
Implement a more robust API method declaration system.
Implement new API methods and signatures.
Implement Session Create/Connect on a single command.
Implement auto sending of PageViews if no other actions are created
Support both API versions

Temp fix to handle both API versions,
while deploying the updated versions of all
necessary components.