Launcher: create empty directory for new projects

[Jacobo Aragunde Pérez]

Version: (2013-01-27 BZR 3925)-testing

A good practice for new projects is to save them in their own new directory, to avoid contamination with external files. It would be great that KiCad actively encouraged this practice detecting if the selected directory contains other files and, in that case, offering the possibility to create a new, empty directory in that location.

[Jacobo Aragunde Pérez (jaragunde)]

Patch to implement this small feature. How it works:
* Checks if the selected directory is empty.
* If it isn't, asks the user if a new directory has to be created.
* In affirmative case, creates a directory with the same name the project has, and saves the project inside it.

I have also done a small modification to simplify the code that appends the .pro extension. If we use SetExt we don't have to check if the extension was already present. If you prefer this change delivered in a different patch, please tell me.

[Martin Errenst (imp-d)]

r3927 stable