enhance Sanitizer.sanitizeForHtml() to filter forward slash

this is because, many XSS attacks use it to close the tag
sanitize for account
sanitize for comment
sanitize for course
sanitize for evaluation
update comment's sanitization
sanitize for fbQuestion
sanitize for frComment
sanitize for fbReponse
sanitize for fbSession
update Sanitizer.sanitizeForHtml(): remove filter for \n and \r
sanitize for instructor
sanitize for student
sanitize for submission
Merge branch 'bootstrap' into Issue2115
try to make dev green
Revert "sanitize for evaluation"

This reverts commit 4aaedc1cf7270c7319356da61cfc8a7ceb76d2e2.
Revert "sanitize for fbQuestion"

This reverts commit 33410e24ef70d0a3d7f91bf0172f71edc5c39cde.
Revert "sanitize for fbReponse"

This reverts commit d245ff8c95e4f8dd84cb856c6592bb85792b8359.
update Sanitizer.sanitizeForHtml(data) to be able to applied for multiple times without breaking data