Integrates quick start for on my own setup

[rtibbles]

• Generates a dummy proquint user name for the on my own setup workflow
• Registers the get_os_user capability to return this
• Fixes oversight where Android API version had not been incremented in the Makefile for system setup

Fixes #133

[nucleogenesis]

Generates a dummy proquint user name for the on my own setup workflow

So it looks like we are checking in the [AppBar](https://github.com/learningequality/kolibri/blob/00010153e3c3329acb3540166819a1c68816d203/kolibri/core/assets/src/views/AppBar.vue#L128) for if the username is a proquint then? In a typical use where we actually get the OS user from the OS, we'll have their Full Name from there and will show that instead of the hashed username.

Curious how you got that username then to show up? Maybe that regex isn't checking for the proquint as I'm thinking?

[rtibbles]

Proquint values are alphabetic - not an alphanumeric hexadecimal, so they're not matched by that regex.

We don't have a full name here either, so having it try to display that wouldn't be helpful either!

[nucleogenesis]

Questions answered - lgtm