Moved customer history add action to validation method.
Merge branch 'master' of https://github.com/opencart/opencart

Conflicts:
	upload/admin/controller/sale/customer.php
Added prevent default action on buttons. Worked fine on Chrome but FireFox caused the page to refresh (inheriting the button submit action for the form)
Merge branch 'master' of git@github.com:opencart/opencart.git