Use helm-maybe-exit-minibuffer where needed, update autoloads.

* helm-config.el: Update autoloads.
* helm-help.el:    use helm-maybe-exit-minibuffer where needed.
* helm-imenu.el:   use helm-maybe-exit-minibuffer where needed.
* helm-mode.el:    use helm-maybe-exit-minibuffer where needed.
* helm-semantic.el:use helm-maybe-exit-minibuffer where needed.
* helm-utils.el:   use helm-maybe-exit-minibuffer where needed.
* helm.el:         use helm-maybe-exit-minibuffer where needed.