Fixed minor issues with wysihtml5 editor

* pressing HTML button now gives visual queues that you're in HTML mode
* changed link icon
* used wysihtml5 v0.4 so that p tags are used on pressing return
Merge branch 'develop' of https://github.com/unikent/programmes-plant into refactor/wysihtml5-fix-issue-125

Conflicts:
	application/views/admin/inc/scripts.php

Also moved the wysihtml5 js files
Merge pull request #141 from unikent/refactor/wysihtml5-fix-issue-125

Fixed minor issues with wysihtml5 editor