Attempted reorganisation/ rewrite

[grum-tez]

Hi, I've attempted to re-organise this page so it is a bit easier to follow.

I have tried to limit new information, and mostly have just reorganised your information and added some comments you have shared via slack.

I make a few claims that might be false. Let me know and I can fix, or you can fix (or of course you may just ignore this PR)

• I claim that the docker install is the binary compiler in a docker container
• I claim that if you install completium-cli, the JS version of the compiler comes pre-installed and if that's what you want to use you don't have to do any more compiler setup
• I claim that to update your archetype version if you are using the JS compiler, you should reinstall completium-cli (and that's all you need to do)
• I describe about the binary compiler as a 'native' compiler to distinguish it from running on docker. Not sure if this is the right terminology.
• I give a summary of the main features of completium-cli under the heading "2. Install Completium CLI" which may be incomplete or incorrect

Other notes:

• I didn't make any changes to the instructions for installing the binary even though these instructions didn't work for me. I guess if you are using the binary install, you probably don't need this sort of step by step guidance anyway and can figure it out.
• I avoided using the word 'version' to describe the different compiler installs, as this gets confusing because the word 'version' is also used to describe the archetype version (e.g version 1.4.1)

A question: After you update the archetype version with docker or binary install, do you have to run completium-cli init?

I always welcome constructive criticism. Equally I will understand if ignore this PR if this sort of PR is not helpful or more trouble than it is worth.