Initial commit
Add USB core to the library
Update libmp.c

* Update do_repl and readline functions
Add FB debug interface

* Add FB debug alternate interface
* Hangle FB control messages
Fix USBD_ITF_MAX_NUM
Disable ID pin config
Add support for executing scripts

* Add function to get the do_repl line
* Add function to interrupt the do_repl
Add support for executing scripts via ctrl xfer
Increase CDC CMD EP size
Use BULK endpoints for script transfers
Fix USBDBG transfer size

* Fix USB transfer size
* Add missing function prototype
* Change callback names to usbdbg
Remove usart
Update MP