Previously if there was a white-space in fn: fn( ) {} we failed to infer no args.

This was originally reported by recht, but I decided to use a different fix.

Closes #829

We have many instances of this object and we clone them as well (e.g. ng-repeat).
This should save some memory and performance as well.

Double prefixed private properties of attr object:
attr.$element -> attr.$$element
attr.$observers -> attr.$$observers

Update shallowCopy to not copy $$ properties and allow passing optional destination object.

The `attr` object was only shallow copied which caused all observers to be shared.
Fixing similar issue in ng-* boolean attributes as well as ng-src and ng-href.

these files are now mostly empty so it doesn't make sense to keep them
separated from other helper functions

Instead of using our custom serializer we now use the native one and
use the replacer function to customize the serialization to preserve
most of the previous behavior (ignore $ and $$ properties as well
as window, document and scope instances).

This breaks IE7 for which you can use polyfill:

https://github.com/douglascrockford/JSON-js

<!--[if lt IE 8]>
<script src="json2.min.js"></script>
<![endif]-->

or

http://bestiejs.github.com/json3/

<!--[if lt IE 8]>
<script src="json3.min.js"></script>
<![endif]-->

$httpProvider.defaults.transformRequest and $httpProvider.defaults.transformResponse
are now arrays containing single function. This makes it easy to add an
extra transform fn.

adding an extra fn before had to be done in this cluncky way:

$httpProvider.defaults.transformResponse =
[$httpProvider.defaults.transformResponse, myTransformFn];

after this change, it's simply:

$httpProvider.defaults.transformResponse.push(myTransformFn);