Default values for lakewalker plugin

[PerroVerd]

When entering in Preferences after installing lakewalker tends to write some default values to .josm/preferences even if you dont enter in teh lakewalker conf.

Some of them are like python executable = python.exe that doesnt work in linux and leads to an error when trying to use the plugin. Also entering again in preferences its not posible because of the same error so the solution its to edit the preferences file by hand and remove the lakewalker lines. After all of that the plugin works like a charm (if you dont enter in preferences never ever again :)