Add default value to partition.conf.

src/modules/partition/partition.conf

@@ -8,3 +8,10 @@ ensureSuspendToDisk:    true
 
 # Correctly draw nested (e.g. logical) partitions as such.
 drawNestedPartitions:   false
+
+# Default filesystem type, pre-selected in the "Create Partition" dialog.
+# The filesystem type selected here is also used for automated install
+# modes (Erase, Replace and Alongside).
+# Suggested values: ext2, ext3, ext4, reiser, xfs, jfs, btrfs
+# If nothing is specified, Calamares defaults to "ext4".
+defaultFileSystemType:  "ext4"