Restructuring FEAT stuff a bit - all FEAT directory speciofic things are

now in a module called featresults.py, which allows query/load of
settings, files, etc.

Also added ability to load an overlay from a FEAT directory (instead of
having to specify the filtered_func_data). But WX does not have a file
dialog which allows selection of either files or directories, so this
new feature can only be done via command line at present.