Makefile: mount/unmount the card when running "make install", including modules
Summary:
- option to specify a command before running "make install" (e.g. to mount the card)
- always unmount the card after running "make install" in modules
- a few other minor tweaks
Hope it doesn't break the usual stuff (make zip etc).
I needed these changes to automate "make install" on my wifi card (the wifi_sd branch), but they should be useful for regular cards as well (in particular, when running "make install" from a module directory, you can no longer remove the card without unmounting it first).