Check every content child

This fixes a compatiblity problem with other extensions
when they add extra html nodes into the content.
Form is not guaranteed to be the first child of content.
Checking every child resolve the issue.
Merge pull request #45 from DeuxHuitHuit/patch-1

Fixing problem when the page's html is changed by other extensions
Version 2.1.1
fix broken xml
Merge pull request #47 from DeuxHuitHuit/patch-2

fix broken xml
Version 2.1.2
Prevent crashing the login page

This fix will check if the user is loggued into the backend
before trying to edit the Administration page html.
version bump + release notes
Merge pull request #50 from DeuxHuitHuit/patch-3

Prevent crashing the login page
Fix inconsistent behavior

@andrewminton found out that on some setup, `$form[0]` would not be
set. Somehow, the first item in the array was at key = 1

So this fix uses php's current method to get the firt item in the array.
Merge pull request #54 from DeuxHuitHuit/patch-3

Fix inconsistent behavior
Update extension.meta.xml
Changed default field location to sidebar
Merge pull request #58 from nathanhornby/integration

Changed default field location to sidebar