Resizing the new session manager

The session manager in latest snapshots is still resizable (which is good) but reserves all the space for the right panel ("Details") while the left panel ("Saved Sessions") has a fixed width. At least in my case, the session name is the only string that can get pretty long (at least, longer than 25 characters) while hostname, username and password normally fit in a small text control.

I think both panels should get resized and keep their relative widths. Or, if that's difficult to accomplish, the fixed width panel should be the one of the right.

Curious, I also thought the same and was unsure which of both list and details box should benefit from resizing. r2610 lets both benefit.