Add track selection

[dantheta]

Tracks describe a path through the questionnaire. The four tracks currently supported are:

• solo dev

• organisation

• new product

• existing product

• solo dev & new product

• organisation & new product

• solo dev & existing product

• organisation & new product

A slide can be added to one of these tracks, and once the user has completed step 1.1 we know which track they have chosen. More detail to follow on a wiki page.

[dantheta]

These are selected using two sets of radio buttons for [solo/org developer] and [new/existing product].

[dantheta]

The first part of this is live now.

Still to do: Load the selected track when the user re-opens a project from their project list. Currently the slidelist in the side menu goes back to showing all steps when a project is closed and reopened.

[dantheta]

Wiki page here: https://github.com/openrightsgroup/alidade/wiki/Slide-selection-(questionnaire-routing)