ENH: Add desktop file

Instructions on the wiki could be updated to saying something like:

To facilitate launching the application, consider doing:
```Bash
$ sudo ln -s ~/VideoMEG/VideoRecStation/Release/VideoRecStation /usr/local/bin/VideoRecStation
$ cp ~/VideoMEG/VideoRecStation/VideoRecStation.desktop ~/.local/share/applications
```
This will enable both command-line launching, and add the application to the Science section.

At some point the icon could be upgraded to something less generic, too.