Get cmd/em from the mingw/msys repo

This is shorthand for starting the right emacs. Not very useful in Linux,
but crucial in Msys; this script provides a common finger-level interface.

new file:   cmd/em
Retain preferences for Eclipse and Netbeans

new file:   .eclipse/eclipse-luna-prefs.epf
new file:   .netbeans/exported-prefs.zip
Make the exported prefs name include the version

I am doing that for Eclipse already.

renamed:    exported-prefs.zip -> netbeans-8-exported-prefs.zip