MDL-42462 - Feedback - Fix for WCAG 2.0 issue with Informational and Error Content Displayed in red

1) The same code used in other Moodle forms is now used in Feedback to display the "There are required fields in this form marked (*/Required field)" message at the top of the screen and each of the asterisks next to required fields.

2) Feedback specific styles (missingrequire, feeback_required_mark), which were used to highlight required and error fields, have been eliminated. These colours are now controlled by the common Moodle styles (mform1, mform, fdescription, required, req and error) that are used throughout the rest of Moodle for a more uniform appearance.

3) Field level error reporting now displays a message instead of just highlighting the field in a similar way that other Moodle forms do.

Affected files:

- /mod/feedback/styles.css
- /mod/feedback/complete.php
- /mod/feedback/complete_guest.php
- /mod/feedback/edit.php
- /mod/feedback/print.php
- /mod/feedback/item/captcha/lib.php
- /mod/feedback/item/info/lib.php
- /mod/feedback/item/multichoice/lib.php
- /mod/feedback/item/multichoicerated/lib.php
- /mod/feedback/item/numeric/lib.php
- /mod/feedback/item/textarea/lib.php
- /mod/feedback/item/textfield/lib.php
- /mod/feedback/lang/en/feedback.php

Signed-off-by: Michael Milette <michael.milette@instruxmedia.com>