export config

Added

• command cc1101-export-config to export / inspect config register values
  after configuration via command-line arguments & options matching cc1101-transmit

Fixed

• cc1101-transmit command:
  • set flock on SPI device file to avoid race conditions,
    if other processes attempt to use the same transceiver
  • configure transceiver after reading from stdin
    to avoid delay between configuration and transmission, if pipe is slow