[Fixes bug #1177749] Add file extension when saving Palette file
[Fixes bug #1177749] Add file extension when saving Palette file

Fenex/Pinta,Fenex/Pinta,PintaProject/Pinta,PintaProject/Pinta,jakeclawson/Pinta,Mailaender/Pinta,Mailaender/Pinta,PintaProject/Pinta,jakeclawson/Pinta