Feature: Cam stream (work in progress)

Refactor: renamed msgs vector -> error_msgs

Refactor: sdk_login() returns an long value rather than setting user_id
Refactor: renamed FLUTTER_ERROR struct to HV_LIB_ERROR

Refactor: renamed FLUTTER_ERROR struct to HV_LIB_ERROR

Fix: passing of user credential and cam address should finally work
Fix: calling play() posts back an success message.
Fix: texture resolution can be passed on calling create_texture()
Refactor: when start streaming causes an error, it will be passed to flutter