Hello World via a tab in the jrEmbed TinyMCE popup

Adds a tab to the popup, inserts a placeholder into the editor text
which is replaced with 'Hello World!' when the text is displayed.
Add icon text, remove hello.php

Removed hello.php - it isn't used
Added "Hello World" text to icon.png
Merge branch 'WiP'
Merge branch 'master' of https://github.com/Ultrajam/JR5-Hello-World into Ultrajam-master

Conflicts:
	include.php