Fix for issues https://opends.dev.java.net/issues/show_bug.cgi?id=4484 and https://opends.dev.java.net/issues/show_bug.cgi?id=4485.

Both issues are related to referrals.  With these modifications:
1. If the user selects to follow referrals and they cannot be followed, an error message appears when the user selects the referral entry.
2. If the LDAP URL in the referral has no host/port specified, the local server is used.
3. An error message is displayed when there is a DIT loop condition (a referral in a server points to an entry in the same server that is an ascentor of the referral entry).
4. The scope and filter of the referral are honoured in a best-effort mode: the first entry of the referral filter is used to 'follow' the referral.  So there is an accepted limitation in this area: if a referral has a filter where several entries can be retrieved, the first entry found is used to represent the node (and thus different refreshes in the browser can make that different entries appear in the place of the referral entry).