[BF] Typos, capitalization, language small fixes - fixes #938

Fix several typos in settings help text. Use the correct capitalization.

In addition to the above, I have:

• ensure unit tests all run without error
• ran pslam and corrected any static analysis issues
• ensured all relevant template output is escaped to avoid XSS attached with <?= $t->ee( $data ) ?> or equivalent.
• ensured appropriate checks against user privilege / resources accessed
• API calls (particular for add/edit/delete/toggle) are not implemented with GET and use CSRF tokens to avoid CSRF attacks

(none checked above since only help text string values are changed)