Explicit set the time-zone for the OTP internal model

[t2gran]

Is your feature request related to a problem? Please describe.

Trying to resolve the time-zone from the data is hard, error prune and difficult to understand. We need the time-zone when processing both street data and transit data. Today we try to fetch the time-zone from the first agency loaded. The benefit of auto resolving the time-zone is that no config or cli parameters are required to start OTP. This is such a small use-case, most people is starting OTP with config, and for those who dont setting the timezone from the command line would be a small change.

The goal with the OTP internal time-zone is to store all data in it. It will be used by the OTP logic, while debugging and in logging. The time-zone used on the API should not depend on it - we are not there yet.

Goal / high level use-case
Simplify OTP maintenance and make a system witch is easy to reason about.

Describe the solution you'd like
The time-zone MUST be set in either the config or at the command line for the first graph build. When a graph is loaded the time-zone is read from the graph, and any config or cli parameters are ignored. If both is set the command-line should override the config.

In build-config.json:

  "time-zone" : "Europe/Paris"

On command line:

--systemTimeZone : Use the server system time-zone  
or
--timeZone "UTC" : Use the specified timezone ("UTC", "Europe/Paris", "-05:00").