Add code to speaker

Add unique identifier (code) to speakers within schedule JSON API
to allow speakers to be identified throughout the schedule.

LCA2022 Setup

Update dates and descriptions for LCA2022.
Remove old miniconf proposal types.
Add local timezone to speaker profile.

Update to Django 2.2

Upgrade site and modules to Django 2.2. Remove and replace obsolete
functionality with current equivalents. Update requirements to latest
versions where possible. Remove unused dependencies.

Add assistance details field to speaker

Add multiline text field to gather details on travel and accommodation
assistance to help with speaker acceptance planning.

Fix absolute URLs, 'Sydney' on the speaker create form

Fix !87

Travel assistance to sydney please

* Tweaks help_text to indicate that travel assistance is to Sydney
* Includes the required migration

This migration doesn't change the DB so it's safe to apply with the system live.

Add the T&C and COC to the accept box

Link to the T&C and Code of conducts so people know what they are
accepting. Create this as a static link because i don't know how django
would accept this being something dynamic on the model.

This annoyingly creates a migration, but it's not a real change and
easier to accept it now than fight django forever.

Taking one out of PyCon's (US) book

We're lock-step with symposion, and upstream is dead.
Vendor it.