Use /usr/local to install GaleForce

This release changes the install method:

• During the recovery image install, we now setup GaleForce in /usr/local/galeforce
• After the install, minimal changes are made to the new root partition (including copying and linking some config)
• The same changes are re-applied whenever an official automatic update is made

Finally, all busybox commands are now linked to /usr/local/bin, so they're ready to use out of the box.