Use protocol-relative links for admin-ajax calls

The plugin uses the admin_url() function to build all of its links to
ajax handlers. This fails under certain conditions: when a site uses
FORCE_SSL_ADMIN, these links are built using https:// as the protocol.

This can cause a number of cross-domain problems, especially in latest
FIrefox and in IE9+. If an https xd_reciever page is used on an http
page, then cross-domain communcation won't work properly. And if an
https url is used as the redirect_uri on an http page, that will
similarly fail in IE10.

The admin_url() function takes an optional second argument, $scheme, and
if an empty string is passed there, it will use the scheme of the
calling page, which is the behavior we want here.
Filter out array prototypes when iterating rel

The function that parses dimensions passed to the colorbox blindly
iterates all properties of an array, without filtering out ones that are
inherited from Array.prototype.

This causes string processing problems in IE8, when trying to split a
"string" which is not really a string...
Avert the Eye of Sauron's gaze

When using legacy (iframe) Capture signin, the logged-in cookies are
supposed to be set from the page specified as the redirect_uri, which
loads in the same iframe as the Capture widget. However, some
configurations of Internet Explorer (which were the default settings up
through IE8) refuse to set cookies from within an iframe, EVEN if the
iframe is on the same domain as the parent page, unless that iframe
sends a P3P (Platform for Privacy Preferences) header containing a
compact privacy policy (CP).

This adds a P3P header to the redirect_uri function. The policy I chose
is the same one that's hardcoded into the Capture widget... it may or
may not be legit, but it works to divert the Eye.

Source:
http://stackoverflow.com/questions/389456/cookie-blocked-not-saved-in-iframe-in-internet-explorer

Also, apply the same trick as in 7f07517 to force the logged-in cookie
to set relative to the protocol of the requesting page.
[EXT-339] added backplane server base url to the admin page

[EXT-339] added backplane server base url to the admin page
[EXT-339] added backplane server base url setting to the widget JS output
[EXT-339] added support for an admin field prefix and added a prefix to the new field
Merge pull request #18 from janrain/EXT-339-Backplane-URL

Ext 339 backplane url
[EXT-363] Make remote screens work

Also got rid of a wtf block in the admin.
[EXT-363] render widget screens uses wp_remote_get
[EXT-363] allow remote stylesheets

stylesheets were only accessible locally.
Merge pull request #19 from janrain/EXT-363-fix-remote-screens

Ext 363 fix remote screens
[EXT-333] Hardcoded registerFlow

also decrappified responseType
Merge pull request #20 from janrain/EXT-333-remove-reg

[EXT-333] Hardcoded registerFlow
[EXT-368] Updated version numbers.

cleared some "we're stupid" style comments.
[EXT-368] Remove invalid tags
[EXT-368] More screen fixes
[EXT-368] Fix social reg screens
[EXT-368] Update contributors
[EXT-368] Clear commented lines
Merge pull request #22 from janrain/release-0.2.3

[EXT-368] Release 0.2.3