Phantom column in library table ---(Bug #1258776) fixed

Bug #1258776 
there is a ambiguous column in library table(actually almost in all table)  in latest git master. which is of "KEY_ID" column. which is not supposed to be there though it is needed for "KEY" column.  
Now i have made this column internal by changing isColumnInternal() function in following files.

 src/library/baseexternalplaylistmodel.cpp
 src/library/baseexternaltrackmodel.cpp
 src/library/cratetablemodel.cpp
 src/library/hiddentablemodel.cpp
 src/library/librarytablemodel.cpp
 src/library/missingtablemodel.cpp
 src/library/playlisttablemodel.cpp 

and Now no more "KEY_ID" column in Tables.
i have added the resulting screen shot.  
![bugfix](https://f.cloud.github.com/assets/5162252/2301142/cacb2842-a128-11e3-985d-87e8778b6b47.png)