Update with new options: hyperDesktop / user layout / emoji layout

Hello all,

There are three additions in this merge request.

hyperDesktop. The purpose of this new layout is to help users maintain muscle memory when migrating from Apple-OS-X to Linux and variants. This has been a tricky process for me, and having got the options as outlined here would have saved me many days of work (c.f. for a write-up https://github.com/bjohas/Ubuntu-keyboard-map-like-OS-X). The 'symbols/hyper' file also has options for making use of the Hyper key in other ways, as well as some options for Level3 switching.

user. For me, understanding how xkb works (and how to apply my own maps) has been quite long winded. As xkb doesn't allow per-user configuration, I thought it would be nice to help people wanting to make changes by providing a 'symbols/user' file. It's minimally populated but appears in 'evdev.xml'. This way users can make changes locally, and select the changed layouts via their windows manager (including improving usability for non-technical users).

emoji. I have added 'symbols/emoji', with the most common emoji (according to various surveys), but also included additional emoji maps. The purpose of this is to be able to enter emoji quickly (via Level3) rather than another add-on.

In developing the above three files, I've tried to be as transparent and explicit as possible. The aspiration is that they are modular and easy to follow, helping others understand xkb and how to make additions (which has taken me a significant amount of time).

base.xml is changed accordingly, enabling both layouts and options. I've added 'BJOERNEXPAND' as markers to indicate where the changes were, but obviously, those markers would be removed.

I realise that this is a fair number of changes - certainly for a first merge request. Very happy to discuss details and make changes as people see fit.