fixed filename

case in base file has to be the same as case in the file system.
Otherwise things go wrong on linux.
add units to designtables
started adding set screws
Added inch sizes to base

To do that:
-Renamed keys to legal design table configuration names (and added
probable thread pitches).
-Added "e_min" column data to hexagonnut3 in nut.blt

Also turned on dual dimensions in the nut.sldprt
Changed default key to be a valid selection from new keys
Updated Nut file naming
Updated default in nut.blt