- widens path fields in the spring options tab of the preferences dialog

This changes the BoxSizer flags so that they expands horizontally to fill the size of the preferences dialog, even when it is resized, and provides the corresponding priority weights accordingly.
yep, its partly miss-used because of the missing checkbox/dropdown/... to select/show the default engine.

this dialog generally shouldn't be needed for a noob user, but to make it good:

some button/checkbox/... is needed to select the default engine and to show the user which one is the default one. without adding this gui control, any change won't really improve it because either functionality is lost or sth. will break.

in this case, disabling this line will make springlobby not show, which is the default engine.