Fix help tooltip for current user member of in event handlers

In Studio, event handlers screen

• Tooltip for current user is member of mentions EL expressions
• But event handlers actually use MVEL

=> Help should be updated to reflect this.

TODO

• In event handlers screen
• Update help label for "current user is member of" with:

Activated only if current user is a member of given group, and since version 5.6, also if user is member of one of this group's children. This is equivalent to using a custom MVEL expression with value "CurrentUser.principal.isMemberOf('groupname')".