[Toaster] Second design proposal - building non-Git layers

[Barros Pena, Belen]

I spent last week gathering feedback from my first design proposal about
how to build non-Git layers with Toaster. For some background, the first
design proposal is here

https://lists.yoctoproject.org/pipermail/toaster/2016-June/004855.html

The main point from the feedback was that the design was unnecessarily
complicated: it provided options that were unlikely to be widely used. It
also allowed users to change the data coming from the layer index, and
that made some people a bit uncomfortable: they thought that data
constitutes a baseline and a safe point of return for users, so it should
be kept "sane".

I agree with both points, so I set to work on a version 2 that addressed
them. A new explanatory video is available at

https://youtu.be/z5wVjBwJDzY

We will be discussing both design proposals in the upcoming design review
call, which is open to everybody. This is your chance to get your hands
dirty with design stuff, if you are so inclined. These are the call
details:

Date: Thursday, July 7th
Time: 4:00 PM BST (8:00 AM PST, 8:30 PM IST)
Tel: 1-888-875-9370/916-356-2663

Bridge: 4
Passcode: 1434913

If you are coming, please make sure to watch both videos beforehand (they
amount to about 15 minutes, so I hope it's not too much to ask).

Video 1: https://youtu.be/N6gvTtZUP3Y
Video 2: https://youtu.be/z5wVjBwJDzY

See you there.

Belén