logplayer-gui: Window title options

[judfs]

Matching the new args added to lcm-spy by #389 :

  -t, --title [LABEL]    Display LABEL in the window title.
                         Defaults to the log filename.
  --title-url            Display the LCM URL in the window title.

The log filename is now displayed in the title if a different title isn't given.

If the file chooser gui is canceled, the app now closes. [I don't see a reason to remain running if there is no other way to select a log].

Example usages:

./lcm-java/lcm-logplayer-gui # Will exit if you hit cancel
./lcm-java/lcm-logplayer-gui loggylog.log 
./lcm-java/lcm-logplayer-gui loggylog.log --title "Alice"
./lcm-java/lcm-logplayer-gui loggylog.log -l 'udpm://239.255.76.67:8888?ttl=1' --title-url