Feature/organizer first day of week

[cornelisonc]

What changes I've made

• I've added a field to Organizers to indicate what the first day of the week in the calendar should be for their events.
• I've added a setting to the Organizer (next to timezone seemed to make the most sense) to control this field.
• In both the back and front end, HiEvents is now referencing this 'first day of week' field for calendar display.
• I've added testing surrounding the field, as well as the calendar display referencing it.
• I've updated the translation files to include the label ("First day of the week") and help text ("The day calendars start on for your events.") for the new first day of week field.

Why I've made these changes

Referencing issue #1353 -- the first day of week in calendars was not consistent across different screens. I've added the setting so users can control it as they prefer, and referenced that setting across the board so it will always display in a consistent way.

How I've tested these changes

• Added automated testing for the codebase (100% passing).
• Edited field under Organization to change first day of week field value; then, review calendar displays in browser across front and back end to ensure consistency (tested with Tuesday and Friday to avoid any potentially stored values -- none detected)

Checklist

• I have read the contributing guidelines.
• My code follows the coding standards of the project.
• I have tested my changes, and they work as expected.
• I understand that this PR will be closed if I do not follow the contributor guidelines and if this PR template is left unedited.

[cornelisonc]

I have read the CLA Document and I hereby sign the CLA.

[github-actions]

All contributors have signed the CLA ✍️ ✅
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[cornelisonc]

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