Give the new user tables the once-over. Strip the current set of methods

from IUserAccountService, we need to define what goes in there. Change
the handler to the generic handler. Adjust migrations, add index

OpenSim/Data/MySQL/Resources/003_UserAccount.sql

@@ -0,0 +1,9 @@
+BEGIN;
+
+CREATE UNIQUE INDEX PrincipalID ON UserAccounts(PrincipalID);
+CREATE INDEX Email ON UserAccounts(Email);
+CREATE INDEX FirstName ON UserAccounts(FirstName);
+CREATE INDEX LastName ON UserAccounts(LastName);
+CREATE INDEX Name ON UserAccounts(FirstName,LastName);
+
+COMMIT;