Removed unnecessary and confusing code.

FieldEditorPreferencePage automatically registers it's PreferenceStore
in its fields, thus this calls were redundant.

Author: infthi

it.baeyens.arduino.core/src/it/baeyens/arduino/ui/PreferencePage.java

@@ -95,12 +95,10 @@ protected void createFieldEditors() {
 	this.arduinoPrivateLibPath = new PathEditor(Const.KEY_PRIVATE_LIBRARY_PATHS, Messages.ui_private_lib_path,
 		Messages.ui_private_lib_path_help, parent);
 	addField(this.arduinoPrivateLibPath);
-	this.arduinoPrivateLibPath.setPreferenceStore(getPreferenceStore());
 
 	this.arduinoPrivateHardwarePath = new PathEditor(Const.KEY_PRIVATE_HARDWARE_PATHS,
 		Messages.ui_private_hardware_path, Messages.ui_private_hardware_path_help, parent);
 	addField(this.arduinoPrivateHardwarePath);
-	this.arduinoPrivateHardwarePath.setPreferenceStore(getPreferenceStore());
 
 	Dialog.applyDialogFont(parent);
 	createLine(parent, 4);