Updated tests to check our admin UIs and no longer verify that using the same field twice will work.

Issue #2106661: Use field_attach_form_validate() and field_attach_submit() to allow complex fields (including File fields!)

Issue #1981212: Refactor generation of #changed_fields into API function (so it could potentially be cached).

Squashed commit of the following:

commit 59877bfc
Author: David Snopek <dsnopek@gmail.com>
Date:   Sun Oct 6 23:15:51 2013 +0100

     * Created test for text fields with multiple values.

commit 223ce9e0
Author: David Snopek <dsnopek@gmail.com>
Date:   Sun Oct 6 23:09:37 2013 +0100

    Prevent removing text from buttons!

commit fac1562a
Author: David Snopek <dsnopek@gmail.com>
Date:   Sun Oct 6 22:59:29 2013 +0100

    Changed the Comment Alter code so that the failing tests now pass! This includes: list_text with the options_buttons widget (both single and multiple), and single text fields with the text_textfield widget.

commit 3cf1b821
Merge: 2c142841 84f450e5
Author: David Snopek <dsnopek@gmail.com>
Date:   Sun Oct 6 22:39:47 2013 +0100

    Merge branch '7.x-1.x' into simpletest-2104967

commit 2c142841
...