Merge branch 'usb-improvements' into advanced

- Change newline prints to also send carriage return
 - Introduce shell module for serial shell with argument parsing
 - Introduce shell command list for compile time command registration
 - Refactor file system commands for shell subsystem
 - Introduce new shell commands:
   - 'help' command
   - 'flash' command to reset into bootloader
   - 'stress' tests CDC serial writes of various lengths
     - optional delay parameter
 - Harden USB handling
   - Hangs less
   - Drops fewer inputs
 - Circular buffers for both reads and writes

Reported-by: Edward Shin <contact@edwardsh.in>
Tested-by: Edward Shin <contact@edwardsh.in>
Tested-by: Matheus Afonso Martins Moreira <matheus.a.m.moreira@gmail.com>
Tested-on-hardware-by: Matheus Afonso Martins Moreira <matheus.a.m.moreira@gmail.com>
Reviewed-by: James Haggerty <james@gruemail.com>
Reviewed-by: Wesley Aptekar-Cassels <me@wesleyac.com>
Reviewed-by: Matheus Afonso Martins Moreira <matheus.a.m.moreira@gmail.com>
Signed-off-by: Matheus Afonso Martins Moreira <matheus.a.m.moreira@gmail.com>
GitHub-Pull-Request: https://github.com/joeycastillo/Sensor-Watch/pull/344

watch-library/shared/watch/watch.h

@@ -88,6 +88,10 @@ bool watch_is_usb_enabled(void);
   */
 void watch_reset_to_bootloader(void);
 
+/** @brief Call periodically from app main loop to service CDC RX/TX.
+  */
+void cdc_task(void);
+
 /** @brief Reads up to len bytes from the USB serial.
   * @param file ignored, you can pass in 0
   * @param ptr pointer to a buffer of at least len bytes