license: Rename LICENSE-lgpl3.txt to LICENSE-LGPL3.txt
license: Add LICENSE-GPL3.txt

In version 3, the LGPL references the GPL, so it may as well be included.
usb: Add Apache License

M-Stack is now dual-licensed with the LGPL 3 and Apache 2.0.
bootloader: Re-license as dual LGPL3/Apache2

The bootloader was previously BSD. Now that the Apache2 license has been
added to the M-Stack core, relicense the bootloader to be the same as the
rest of M-Stack.