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

A & B: Modifies CSS code in the following files to make the colours WCAG compliant:

- /mod/feedback/styles.css
- /theme/standard/style/core.css
- /theme/standard/style/modules.css

Colours were selected to be match the colours used in mform of the base theme.

C: The ABBR tag was wrapped around the asterisk and a space was added between the text and the asterisk in the following files:

- /mod/feedback/item/textfield/lib.php
- /mod/feedback/item/textarea/lib.php
- /mod/feedback/item/numeric/lib.php
- /mod/feedback/item/multichoice/lib.php
- /mod/feedback/item/multichoicerated/lib.php
- /mod/feedback/item/info/lib.php
- /mod/feedback/item/captcha/lib.php
- /mod/feedback/complete.php
- /mod/feedback/complete_guest.php

Signed-off-by: Michael Milette