Add sudoers template
Ignore test directories
Add --tftp option
Improve U-Boot support

- U-Boot prompt is configurable
- Allow multiple --uboot-init options
- Do not try to boot if there is nothing to boot specified
Detect errors when starting tftpd

No we start tftpd without forking in novaboot (but in tftpd itself), which
allows us to detect when it does not start correctly. For example when
a system daemon already runs.
Inform the user in interaction is only onedirectional
Add --tftp-port option