Make depth unit configurable

[bkeepers]

After #11, it will show meters for everyone except browsers with navigator.language set to en-US. This should probably be a setting in the plugin config.

[PiotrSol]

Please also allow time format to be configured or accept-language dependant.
All but en-US should use 24h 4 digit time, standard format in navigation (I beleive US call it military time).

[PiotrSol]

All fine in ver 1.2.3 - metric and 24h clock
Thanks!

[Peter-Petrik]

This should probably be a setting in the plugin config.

Will you be implementing a configuration setting to choose units (ft/m) and time format? My browser is en-US but display preference is in meters and 24f time. I'm running v1.4.0