Don't display smart tags on empty interface

Also filter out duplicated members.
Fix #828.
Add VS unit tests for implement interface
Add a simple way to recognize fully-implemented interfaces
Fix AppVeyor build
Merge pull request #890 from dungpa/empty-intf

Improve implement interface feature
Bypass unsupported attribute arguments

Close #831.
Use current module/namespace as an implicit open declaration

Fix #832.
No longer display 'AttributeUsage'.
Merge pull request #891 from dungpa/unsupported-attributes

Bypass unsupported attribute arguments