Split node keys into .pub and .priv files
Split node keys into .pub and .priv files

Also refactor the loading etc. a bit so that we can more
easily read and write the two different files, and add
logic to confirm they're consistent (i.e. that the public
key really corresponds to the private one).

NinjaMSP/crossbar,w1z2g3/crossbar,NinjaMSP/crossbar,w1z2g3/crossbar,NinjaMSP/crossbar,w1z2g3/crossbar,w1z2g3/crossbar,w1z2g3/crossbar,w1z2g3/crossbar,w1z2g3/crossbar