Fix: Add missing trim() when fetching 'content' block

Without trim(), an empty line will activate the block and cause
the table contents not being rendered.
Fix: Determine valid actions for Wysiwyg.wysiwyg.js inclusion

Closes #554, #555

Signed-off-by: Rachman Chavik <rchavik@xintesa.com>
Add Admin.spinnerClass() and remove hardcoded icon codes
Meta: Use the default input class in helper