Some invites are not suitable for creating a new account

Merge branch 'any-colour-theme'

* any-colour-theme:
  Any colour theme

Any colour theme

Allow a "custom" theme which can be set to dark or light basis and have the
three main colours set to any colour at all.

Allow adding the "Go" button even if there is only one fillable field

Merge branch 'just-one-list'

* just-one-list:
  Synthesize default option for custom value in button grid
  Support button grid for boolean field as well
  Force immediate loading so that the button values don't repaint
  Show SVG icons in button grid
  Only use local label if there isn't a custom one
  If there is only one list-single field, render as buttons

Allow any ListView like item to nested scroll up and down

Clear items before adding more

Allow creating account for myself using invite

Fix invite qr code

Synthesize default option for custom value in button grid

Support button grid for boolean field as well

Force immediate loading so that the button values don't repaint

Show SVG icons in button grid

Only use local label if there isn't a custom one

If there is only one list-single field, render as buttons

If there is only one (non-cancel) action and only one field and it's a
list-single then let the user just tap the option they want to continue instead
of choosing something and then tapping next.

Table view tweaks

Allow plus unescaped

It is not special in XMPP URIs

Merge branch 'action-buttons'

* action-buttons:
  Support custom actions defined by a special list-single

Merge branch 'onboarding'

* onboarding:
  Start cheogram.com register on first setup if no other PSTNS/SMS gateway
  You need to sign up, no matter what for

Fix NPE