Refactor css used in examples & guides

After some problems with examples, detected by @davidmanzanares, and a discussion with also @elenatorro on the use of css & examples, let’s improve its use.

These are the main points we have talked about:

1. We clean / refactor style.css a bit to remove unused styles (which is always fine… 😄 ). IMO we should rename it to examples.css to remark it is not official, just a help for the examples.
2. We create a basic.css or setup.css with just the minimum css (no panel, no title… nothing, just the bare map) , solving the problems fixed by David at https://github.com/CartoDB/carto-vl/pull/1040
3. We talk a bit in the getting-started guide about what is the basic.css and examples.css, telling the people how to reference them or just copy & paste their code in their on-going work
4. We reference the basic.css if we want to use & explain very simple examples for the guides (eg. getting started or sources guides).
5. If the example for the guide requires panels, with title, paragraph… we use the refactored examples.css
6. If the example needs custom / advanced styles, we create a different, specific css for it (either in style or external, but explained in the corresponding guide). We keep the reference for the examples.css with the common stuff.
7. We always add examples.css for non-guide examples, as they always have a panel with a title

[VictorVelarde]

I would say so, I’ll close 1057, cause this has more details

[VictorVelarde]

That’s my point. IMO it should be an optional helper, not THE ‘carto-vl.css’ file (maybe we could call it ‘basicViz.css’ or so?). And I would just include there the basics for a full screen map + basic panel.