Replace preference manager set / get methods with templates
Add preferenceDidChangeNotifier to PreferenceManager

Signed-off-by: Kristian Duske <kristian.duske@gmail.com>
Fix a minor memory leak.

Signed-off-by: Kristian Duske <kristian.duske@gmail.com>
Add preference dialog

Signed-off-by: Kristian Duske <kristian.duske@gmail.com>
Hook events for general preference pane
Refresh map view when a preference changes

Signed-off-by: Kristian Duske <kristian.duske@gmail.com>