config: rename Set_config_defaults() to Prepare_config()

it mostly applies defaults where a value does not exist, but does more in
some cases. the new name better reflects its usage and functionality.

Gbp-Dch: Short

functions/defaults.sh

@@ -69,7 +69,8 @@ New_configuration ()
 	export LIVE_IMAGE_TYPE
 }
 
-Set_config_defaults ()
+# Prepare config for use, filling in defaults where no value provided for instance
+Prepare_config ()
 {
 	# FIXME
 	New_configuration

functions/init.sh

@@ -28,7 +28,7 @@ Init_config_data ()
 	Arguments "${@}"
 
 	Read_conffiles $(Common_config_files)
-	Set_config_defaults
+	Prepare_config
 }
 
 # "Auto" script redirection.

scripts/build/config

@@ -937,7 +937,7 @@ then
 fi
 
 # Setting and validating config
-Set_config_defaults
+Prepare_config
 Validate_config
 
 # Creating or updating saved config