Remove data-action attribute in buttonEnabler

fixes #701 on github.

The 'Add Tree' anchor tags use a 'data-action' tag to enable the add tree mode. The button enabler removes this action in the case of disabling or redirecting, in order to prevent this behavior from leaking through.
Add google analytics and setting. Fixes #236.
Use registration form to prevent duplicate emails

Fixes #725.

We enforce this both at the database level, and here, using django
registration's ready-made form class.
Merge pull request #737 from steventlamb/bug/701/add_tree_not_redirecting

Remove data-action attribute in buttonEnabler
Fixup whitespace
Add SUPPORT_EMAIL_ADDRESS to settings

Fixes #676.

This was already wired up in some places- but it hadn't been
defined. Now it should be used everywhere where a contact/support email
is needed.
Merge pull request #740 from ahinz/fix/676/support-email

Fix/676/support email
Merge pull request #738 from ahinz/fix/236/add-google-analytics

Add google analytics and setting. Fixes #236.
Merge pull request #739 from ahinz/fix/725/duplicate-email-checking

Use registration form to prevent duplicate emails
Merge pull request #749 from maurizi/master

Add name to user url for use in reverse url lookups
Add "spinner" image
Merge pull request #754 from RickMohr/spinner-image

Add "spinner" image
Style the not-available page

This page may show up a lot in our beta period if people share links to
their beta maps, which can not be made public.
Merge pull request #752 from jwalgran/topic/style-not-available

Style the not-available page
Fix footer/content layout bug, Fixes small label bug
Add "spinner" image
Style the not-available page

This page may show up a lot in our beta period if people share links to
their beta maps, which can not be made public.
Merge pull request #756 from mtedeschi/topic/beta-signup-styling

Beta signup styling
Refactor and DRY out registration

This makes it easier to extend registration without having to duplicate
all of the code again
Revert only showing elements with content in them, Fixes #757

43c12d237e attempted to only show elements when there was content in them,
which broke the UI in several other interesting ways.

Instead we will handle this in CSS with :empty, which is why all error
elements have carefully had spaces removed from them.