fixed "Unknown or bad timezone" issue

[emrysr]

see:
https://community.openenergymonitor.org/t/dashboard-loggedin-vs-public/11626/31

added User\default_timezone
stopped User\get_timezone() from returning false
User\get_timezone() now defaults to default_timezone

the requests for dashboards don't currently include a guest user's timezone. Only logged in users can specify a timezone (set in their account page)

using this pull request you can add a default timezone to your settings file. eg.

default_timezone = 'Europe/Paris'

not currently set in the default-settings file needs testing with different setups first

must be a value supported by PHP: https://www.php.net/manual/en/timezones.europe.php

and the time calculations will use this offset instead of UTC
https://github.com/emrysr/emoncms/blob/c68e9ff887376c85dce1f2984079cc4f166b4196/Modules/process/process_model.php#L30-L49

[TrystanLea]

Thanks @emrys for the pointers to this problem. It's possible to get around this issue another way in the virtual feed engine itself by selecting the userid from the feeds table. I've committed a fix using this approach here:

See: ab04267