PreferenceInitializer - replace by default initialization

[eselmeister]

Eclipse offers an extension point to initialize preferences. This is used widely in ChemClipse via the plugin.xml, e.g.:

   <extension
         point="org.eclipse.core.runtime.preferences">
      <initializer
            class="....preferences.PreferenceInitializer">
      </initializer>
   </extension>

The drawback of this approach is, that

• it duplicates code
• one can forget to add the extension via the plugin.xml
• the bundle must be a singleton when using the plugin.xml (;singleton:=true)

Hence, it shall be replaced by an implicit approach to initialize the preference values.