dev: default for collaborators based on active maker count

[theborakompanioni]

As a developer new to the project, it is not obvious that one needs to adapt the default collaborator count (randomized between 8 - 10) to 1 or 2 (as this is the active makers that are started when running npm run regtest:init). Otherwise the collaborative transaction will always fail.

It should be more obvious to know what to do, e.g. either by setting the default to be 1 or 2, or by providing another visual hint in the UI when the app is started in dev mode (npm run dev:start).

[editwentyone]

default just to 1, 2 or input field as selectable options and add an orange "dev" tag at the title above ?!