Unified the feedback text validation for client and server side

Before that the text was only checked for length on the server
side, while on the client side it was only checked if it was there
at all. Furthermore, the error text is now lexically correct.
Removed the misplaced padding declaration.
Generated handheld RTL styles with autortl.
Merge branch 'wpcom' into feedback-form-react

Conflicts:
	class-draft-feedback.php
	js/feedback-form.js