* add nexa remote support.
This is inspired by: https://github.com/sui77/rc-switch/pull/124
As described there: "The remotes sold in ClasOhlson in scandinavia have
a slightly longer sync sequence(added a skip pulse field in the
protocol) and a 64 bit code word. Part of the code gets lost but that
seems to be OK until support for 64 bit codes is added."
* add default value to ctor
* allow 64bit codes
* lint
* make vars 64 bits
