Replace null layout in dialogs with SpringLayout.

This pull request replaces the null layout manager (absolute positioning of widgets) with the SpringLayout manager within the dialogs in the net.ftb.gui.dialogs package.

This allows to arrange the widgets in a way that considers the different dimensions of the localized labels without calculating the widget bounds by hand. This issue exists also with the english localization like you can see in this picture:

![AdvancedOptionsDialogRef](https://f.cloud.github.com/assets/84891/90443/8dfcd3dc-6576-11e2-87d5-07b9e09e12ac.png)

With the SpringLayout the same dialog looks like this:

![AdvancedOptionsDialog](https://f.cloud.github.com/assets/84891/90445/999c08a2-6576-11e2-9656-c2029d4d09c3.png)