Typo correction in json of settings keys command (was invalid json).
Added command to get firmware version in json, as well as log status.
Use CPM with dead time compensation for all standard output. Removed the
three separate cpm-related commands on the serial interface: getcpm now
returns everything in one structure - our link is at 115200, this is not
an issue at all.

Better documentation on Geiger.cpp
Implement {"get":"cpm"}, remove commented-out code (that' what git is
here for, no need to leave old commented stuff laying around)
Merge pull request #60 from elafargue/deadtime

Deadtime
Merge pull request #58 from elafargue/serialpart2

Serial, part 2
Bugfixes mainly.