Time Command for ECET, BCMT and Local Time

[fvalka]

Add a new command which determines the timezone of an airfield (probably based upon its coordinates) and based open this provide the current local time.

Additionally based upon the day the ECET and BCMT can be calculated using an appropriate model for the suns position. For example the following library could be used for calculating the ECET and BCMT:
https://github.com/shred/commons-suncalc