config: fix --config-dir logic for global config files

Global config files should be loaded only when --no-config is missing
_and_ --config-dir is not set.
config: don't load global config files with --config-dir

This sidestepped the usual logic by hardcoding the path.
lua: add option to disable auto-loading of lua scripts
msg: add --msgtime option to add timestamps to each output message

Will be helpful to track down strange wait times and such issues, as
well when you have develop something timing related. (Then you may print
timestamps in your debug output, and the --msgtime timestamps will help
giving context.)
timer: add utility function to get relative time