Add option to bypass Y/N confirmation when applying TF changes

[Mo Balaa]

Would be nice to not have to confirm Y/N for applying each terraform state, especially when deploying a new environment.

[Xu Wang]

@thebalaa: if you add export CONFIRM_TF_APPLY=NO, and source envs.sh, you will not be asked for confirmation when terraform applies changes. For production, you might want to leave it to default YES.