allow using env var PAYMENTDCFG to set config file name
config duration in human-readable format
authorization: allow updating of system password
Merge pull request #17 from wongak/config_loading

Config loading
Merge remote-tracking branch 'upstream/master' into set_system_pw
refresh auth method
tests: test full routing
Merge pull request #18 from wongak/set_system_pw

Set system pw
Merge branch 'master' into paymentd_merge
add marshal required int 64 test for json
doc comments
handle errors more gracefully, add init payment tests