[enc28j60] register definitions fixups
[enc28j60] buffer and mac initialization
[enc28j60] raise SPI speed to 12 MHz. Seems to improve PHY access stability
[enc28j60] enable packet reception interrupt
[enc28j60] add 'on packet received' event registration
[enc28j60] add 'on packet received' JS binding
[enc28j60] ack phy interrupt once
[enc28j60] receive logic - read and parse packet header
[enc28j60] add receiving packet length & data
[enc28j60] js binding for receiving packet data
[enc28j60] mask rx packet interrupt until packet is processed
[enc28j60] packet transmit logic
[enc28j60] bugfix - release reference to array buffer - array buffer view should be the sole owner of the buffer