Week 0 - structural and content revision, plus basic QA

[AndrewB9lab]

This PR provides revision of the Week 0 content to improve its readability and remove duplicated information; it also provides basic QA review. It impacts the following sections:

• Week 0 LP
• 1-blockchain (Blockchain 101)
• 2-public (Blockchain History)
• 3-managed (Public and Managed Blockchains)
• 4-consensus (Consensus in Distributed Networks)
• tutorials/1-tech-terms/index (Good to know dev terms) (QA only)

Change scope

The changes in this Pull Request include (please tick all that apply):

• [X] Small language/grammar fixes
• [X] Small content fixes
• [X] Addition of new content
• [ ] Sample code/command updates
• [ ] Platform fixes
• [ ] Other

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