Fix Markdown and file issues

[ChrisChinchilla]

There are a lot of markdown issues including:

• Incorrect heading levels
• Unnecessary whitespace
• Duplicate files
• File names with special characters such as commas etc
• [x] Broken links

It's hard to list all exact issues, but each file should be swept for potential issues and added to this PR (https://github.com/ethresearch/eth-wiki/pull/27) so we can track progress.

[ChrisChinchilla]

@therealyingtong here's one you might like to help with

[ChrisChinchilla]

There are markdown linters that can help you check these over, and even maybe fix some of the issues. I use remark and markdownlint.