Keep accepted ports in .TORRC not covered by exit template

[vidalia]

This is mainly inspired by the resolved 333. At the moment additions to the exit policy list made by user outside Vidalia are discarded when .TORRC is saved again due some parameters being changed inside Vidalia.
Example: if I currently have set exit policy to only "instant messengers" in Vidalia, add by hand port 5223 to .TORRC, then run Vidalia, change for example the allowed bandwidth and save then I get the standard "IM" exit ports, effectivly undoing the modification I made previously to the policy.

Vidalia already does a great deal parsing .TORRC (even adding comments to several parameters), would be nice if also the exit policy would be checked so that unknown ports wouldn't be overwritten. Ideally the GUI could include some sort of indicator which would hint that the configuration file features settings which affect TOR's behaviour, but aren't configurable/supported by the GUI (Vidalia).