[twgit] Init feature 'feature-105': Add command twgit feature push.
add function twgit feature push
add push to demo and hotfix
add completion
Update help messages. #105
Clean all cmd_push() functions.
Remove unnecessary code in cmd_push() functions.
Restrain "twgit feature push" to feature branches.
Restrain "twgit demo push" to demo branches.
Restrain "twgit release push" to release branches.
Restrain "twgit hotfix push" to hotfix branches.
Merge branch 'feature-105' into release-1.13.0