Add customization types for outline-minor-mode

Altered items:
ox-outline-level, ox-outline-regexp, ox-outline-heading-alist
Set outline vars to ox-outline vars

Altered items:
ox-mode, ox-batch-mode
Add option for toggling outline-minor-mode

Also set default for other outline-minor-mode options.

Altered items:
ox-outline-level, ox-outline-regexp, ox-outline-minor-mode, ox-mode,
ox-batch-mode