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/6

* Same fix as in [6.2.x](https://github.com/noellekimiko/liferay-plugins/commit/7788a56e178100906070fab192eaf9b5c3c20110) and also the fixes in liferay-portal-ee
* Tested with a bundle built from https://github.com/liferay/liferay-portal/commit/e51fd63e071063c9f68bc3f772485170f8d8b854
* 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 narrower page widths in all browsers except IE 8
![responsive buttons after](https://cloud.githubusercontent.com/assets/6542536/4258523/2a25e79c-3ad4-11e4-9841-759c1fa96dcd.png)