Add Paypal Donate button

[heatherleson]

We have investigating our 501C status and licenses. HOT can now have a DONATE button our website.

Tasks:
1.collaborate with Kate and Mikel to add the button
2. size button
3. add to get involved page

Please note - outreach and campaigns will start at a later date. For now, we just want the tech in place.

[harry-wood]

Could do it as on new 'donate' page. Then we can do a test payment... see if it works. And (only when ready) link the new donate page within the navigation of the website.

[xamanu]

This was already done on the D6 site. I added the site to the D7 dev site as well. And this issue can be closed.