Allow to specify the server Timezone at egg level

[QuintenQVD0]

Changes

• Allow a server to set a time zone that is not the same as the one in that wings config
• This is done with the env variable SERVER_TIMEZONE
• If it does not exist then it will use the time zone out of the wings config
• if it exists but is empty it will still use the wings config one
• if it exists it does a check with the time library if it is a valid timezone, if it is it sets it to the TZ variable if not it falls back to the wings config one

This maybe not that useful for now (for some it will), but if the panel add-ons feature is there you can just make a fancy UI for it

Screenshots

ENV variable does not exist

ENV exist but is empty

ENV with invalid timezone

ENV exist with a valid timezone

[parkervcp]

LGTM