chore(ckeditor): upgraded CKEditor to version 4.3.2

Fixes #6500
chore(ckeditor): adapted plugin to work with CKEditor 4

Theme changed to moono, so removed specific BootstrapCK-Skin CSS
CKEDITOR.basePath wasn't working for plugins, so defined CKEDITOR_BASEPATH
Fix applied in #5689 is no more required
Wordcount own code replaced by wordcount plugin
Set allowedContent to true to do not filter tags (htmlawed already does it)
Configured new AutoGrow plugin
chore(ckeditor): more semantic strings in CKEditor interface

Refs 9a17024dc40af139c9a4911c32ba8e2703c032f0 and
4dd8301ab9d7d45913d51db9ba4a9868698bfd12
Merge pull request #6511 from sembrestels/ckeditor4

Ckeditor4 upgrade