Rewrite CSP Errors handler

- Add in exception handlers, responses, etc
- Self-handle all of this without requiring functions.php
- Convert all header keys to lower case
- Check content-type, content-length, and HTTP_HOST
- Check contet-type using RegExp
Enable report-uri & remove %NONCE%

Re-enable report-uri to log CSP Errors
Do not allow nonce in style-src or script-src