Allow primary topic to be null

We hide this field.

LCA2022 Setup

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

Update Miniconf Proposals

Add extra questions to SysAdmin Miniconf. Update wording for ticket acknowledgement.

Add LCA2021 Miniconfs

Setup proposal types for miniconfs at LCA2021.

Add LCA2020 Miniconfs

Setup proposals for miniconfs, including model, forms and admin.

Remove LCA2019 miniconf proposal types

Remove models and forms for miniconf specific proposals.

Supply a default value for target_audience for the ART+TECH miniconf

* The base model requires a value here
* But we aren't using one; so there's none on the form
* This change supplies a custom enumeration that's specific for this
particular model, which has one value, which is a default value,
which simply says that the field is N/A
* This does mean that when viewing or reviewing the proposal one sees
the Target Audience field, but it will say N/A.

* Testing has shown that this does not affect the other types which
descend from the base Proposal class; they still use the default
enumeration.

Finish adding models/forms/admin for new miniconfs

NB: all the proposal sections for the miniconfs here are set to open
on 2017-11-01. To make them available sooner, visit
/admin/symposion_proposals/proposalsection and change the start date.

(re)create miniconf proposals

This is a partial revert of 6d864e8ce56b8cbb53c90c620729238181c6c8ae
- plucking out the bits we want to re-use

Add release materials check boxes to miniconf proposal

We need to have people who are submitting a miniconf proposal agree to
releasing the material. The easiest way to do this is to just make it a
proposal like the other two types. We don't have audience type for
miniconf, instead of deleting it just have a default - it's easier.

WARNING: This requires a real migration to be performed before use.

Use Linux Australia for release and not pycon

Update the recording and materials release to say Linux Australia, not
Pycon Australia. This generates a migration because the model text has
change - but also because in the 0001_initial migration it appears that
this help text is stored as a byte string.

This is a bit weird, but realistically running this migration is not
going to cause us any problems so just add it so we don't end up
fighting django along the way.

Cleanout conf-specific proposals.

We don't have these mini-confs (yet).
We don't want these files.
We're not going to rename the release in 0010 and drop all the extra
tables in 0011, we're going to toss them on the cutting room floor and
call it good.

They're in git, we can look at this commit and past ones on how to
recreate these for new proposal additions going forward.

Mass style-check update

Seems okay.

Form for Open Hardware CFP (#85)

More cfps (#75)

* Law, Testing and Knowledge Miniconf CFP

* Admin registration for latest CFPs

Fixed CFPs using wrong base class (#71)

* Games Miniconf CFP

* Fixed CFPs using the wrong base class

Games Miniconf CFP (#70)

CFPs that are ready (#68)

* CFPs that are ready

* Updated choices for sysadmin

Updates proposal forms and review template (#14)

* Updates the forms and models for Proposal Bases

* Proposal review templates only display fields relevant to LCA

* Display total votes properly

Adds new proposal types for Tutorials and Miniconfs (#9)