LDAP information is not refreshed on re-sync

When you re-sync the FishEye userbase with LDAP, user attributes (e.g. email) are not updated in FE.

To Reproduce:

1. Integrate with LDAP
2. Check the email address of one of the users in FE.
3. Change that users email address in LDAP
4. Resync the userbase in FE
5. Check the users email address again, it will be the old value.

Our solution is to add a radio button set to the 'LDAP Authentication Settings' page, and to the 'JIRA or Crowd Authentication Settings' page.

It will have the title: "Display Name and Email Address Changes" and two radio buttons, the first reading "Update from LDAP on synchronisation and disable local editing." and the second reading "Update from LDAP only on creation of a new user, and allow local editing." (the captions will read "JIRA or Crowd" instead of LDAP on the 'JIRA or Crowd Authentication Settings' page)

On the 'Profile & Email' tab of the user Settings dialog the Display Name and Email Address fields will be disabled, and a message "Your user details are held externally, so your email address and display name cannot be edited in FishEye/Crucible." will be displayed when the first radio button is selected.