Remove some old commands
Merge remote-tracking branch 'pbarker/pvoutput'
PEP8 cleanups
Assorted idiomatic cleanups to pvoutput code

This makes various cleanups to make the pvoutput code match modern Python
idioms.  Changes include:
  * Using True/False instead of 0/1 for boolean values
  * Using list comprehensions instead of map
  * Using string methods instead of the string module
  * Removing some redundant imports
  * Using explicit sys.exit() instead of builtin exit()
  * No extra parens around if conditions
  * Use Python truth-value conventions instead of explicit len() checks
  * Fix some non-standard indent levels
Small cleanups to pvoutput config handling

Config file path is never used outside __init__, so don't store it in the
object.  Parse out the apikey and hostnameport in __init__ rather than
leaving it until we actually use it.
Ensure print_function is used everywhere
Use relative module paths in config module

Allows the test/example code at the bottom to actually execute.
Convert config file handling to JSON
Move config handling from pvoutput org module to config module
Move database opening to config module

Greater consistency with the way inverter and pvoutput connections are
done.
Change default config file name

Since we've totally changed the format.
Fix handling of serial number

Shouldn't really be treated as a decimal, should be treated as a string.
Update sma2-explore for new names

Well, not that new, but it apparently hasn't been updated in a while.
Add some more information to protocol.txt
Attempting at getting historic daily totals
Move inverter config handling into inverter config object
Introduce "systems" to the configuration