FORUM-764 | [Answer] XSS vulnerability in Author Field

Conflicts:

	answer/webapp/src/main/java/org/exoplatform/answer/webui/popup/UIQuestionForm.java
FORUM-682: Separate i18n keys for the links to private post and private message
FORUM-888: [Forum] Escaping in Send Notification's i18n labels

Problem analysis:
* In the input message of Send Notification scripts there are i18n labels.
  These labels in some languages might need to be escaped following JavaScript String rules.

Fix description:
* Implement getLabelEscapedJavaScript method to escape characters following JavaScript String rules
* Use this new method before initializing Send Notification in JavaScript.