[maple_upload] Improve script on linux and macosx

[GrantM11235]

This makes it possible to recover if upload-reset isn't working, for example if a board is running a sketch without USB CDC enabled

Changes:

• Uncomment set -e
• Ask the user to manually reset their device if upload-reset fails
• Retry dfu-util if no device is found
• Print periods while waiting for serial port
• Exit with an error if script times out while waiting for serial port
• Send all messages to STDERR

[GrantM11235]

Thanks for the review!

Let me know if I should squash those fixes in to the first commit or if I should squash everything to one commit.