Support pause/resume video

[asam139]

Problem

• The session was ended on pause method so when the video was resumed it threw an exception

Solution

• Don't end session on pause
• Add pause & resume times to the states so the time generated by CoreEngine can be adjusted so the video is created without any gap.

Improvement

• Avoid render while the video is paused: to implement it properly the framework would need a refactor so the input are paused not only the output.

Resolves

• Resolves #61