Attempt to clean up persistence model

Extra commit, will probably go for the union model.

Category: crap
Runner runs

Speed-test was 100K Sample/s for 4 signals. Gathering from sysfs will not
add much overhead and code is not optimized neither lexical nor wrt flags.

What will take time are print outs however, which will take performance back
a factor 10-100. Having debug prints show the difference and simulates
somewhat the same amount of data. Add to that is sending the stream over
USB/TCP/IP...It's still a factor 1000-10000 than scripts and gives much
better control over the temporal domain, but getting up to 100kS/s is not
likely unless writing to RAM-buffers (and in binary form). Perfectly doable,
but will be awkward to get out and to run for longer than short bursts.
Limit it's not really a problem, just curious to figure out the limits. 1KHz
with high control over time, jitter and precision will do just fine.

Category: fun