LPS-40606 OpenSocial Gadget Publisher updated to use <aui:button>

Jira ticket: https://issues.liferay.com/browse/LPS-40606
Alternate solution to: https://github.com/noellekimiko/liferay-plugins/pull/5

* Tested in Chrome, Firefox, and IE 8 - 11
* By changing the <input> tag to an <aui:button> one, the buttons are now styled with bootstrap and are easier to maintain.
* Also, buttons are now responsive to the width of the page in all browsers except IE 8