Create an UI to set users access to tag/email accounts
Disable closing of ticket by unprivileged users
Limited under-privileged user acces to only allowed E-Mail accounts
Allow only admin to access/modify tags and respondents taxonomy
Limited permissions of under-privileged users

A) Now user need access to atleast one E-Mail account to create ticket.
B) User with access to a E-Mail account can access all tickets under it
C) User with access to a particular tag can view/modify only those tickets
Added comments to explain limit_user_permissions() method
Removed accidentally added extra character from HTML
Using class instead of inline CSS
Adding support for I18n in permission setting page
Using labels for form elements
Disable checkbox while AJAX request is processed