Auto save project file

[maks]

It absolutely sucks to lose work. Auto saving at regular intervals would help with that, eg. in case of firmware crash or the battery dying or the user accidentally turning off the picoTracker.

I would expect to implement this by auto saving to the project data file to an alternate name, eg. autosave.dat and then delete that autosave file when a user does an explicit save on a project. Then, if a project is opened with an existing auto save file, it means it needs to be used instead of lgptsav.dat.