remove stray callback invocation

This was a leftover from a previous code reorganization and does not
serve any further purpose.
Add --verbose to the ota command

Normally, any unexpected output (errors) are displayed. Adding --verbose
causes all commands output to be displayed, except for the block
commands. When --verbose 2 is passed, also the block commands are shown.
Add comment about ota block size
Print a message on ota failure
Add a delay after sending the scout.otaboot command

This allows the bootloader to start up after the reboot.
Return proper exit codes for ota
Don't hang indefinitely on ota if scout doesn't respond

Before, if the scout wouldn't respond with "OK" or "FAIL" (for example
when it didn't understand the OTA commanfs), the pinoccio command would
hang indefinitely.
Add ota.default-target config value
Add ota --ide option to improve (error) messages

This provides a bit more guidance for people running from the Arduino
IDE.