Indexes in Object Explorer are not shown properly, including primary key indexes

[samir-puranik]

Problems no. 4 and no. 5 from issue #343

• If the index happens to be part of a unique key constraint, the only right-click option for the index is Refresh. Script as Create is not offered for unique key indexes.
• And primary key indexes aren't even shown under the Indexes folder

[samir-puranik]

Primary keys will be shown not under indexes, but rather under the constraints folder