description
This is just a normal ol plugin; NOT ftplugin (there really should be a plugin option in the type field when adding a new script... *hint* *hint* :) ) 

This is a quick/simple implimtation to delete duplicate lines (:DDL) and delete blank lines (:DBL) 

Both commands can take a range and DEFAULT TO THE ENTIRE FILE. 
Both of these commands delete lines so be carefull! 

:DBL (delete blank lines) is little more than a command front end to a :g command. 
:DDL (delete duplicate lines) opens folds,  starts at th top of the range and goes down. For each duplicate line found it is :delete 
End result is you can select a portion of a file and quickily and easily delete blank lines and or delete duplicate lines.
 
install details
Install: 
Drop the file into your PLUGIN folder (not ftplugin!) 

Uninstall: 
Simply remove the file. 

To Test drive: 
Just install and :DDL &&|| :DBL some test file. Uninstall if desired.