create capability for specifying custom maps folder

Mark,
Being that I'm working from a fork, the git commands are a bit different, but I did get it to rebase with spatialite_rasterlite2, so they should merge fine.   For prosperity, here's what I had to do:

git checkout mapsDirSettings
git fetch upstream
git rebase upstream/spatialite_rasterlite2
.. fixed strings.xml 
git add geopaparazzi.app/res/values/strings.xml
git rebase --continue
git branch mapsFolderName
git checkout mapsFolderName
git push origin mapsFolderName


Removing the line might make sense. The primary reason for keeping it is to give the user the ability to clear their choice if they change their mind. But then they can just cancel out of the routine or type something in the editbox.