JS1 Improvements from London

[ChrisOwen101]

These are the improvements that we made in this run of teaching JS1 in London. This includes mostly

• Moving the exercises into the content so their easier for the students to find
• Updating the homework so all the homework exists in js-exercises
• Removing Git from JS1

[ChrisOwen101]

I'm having to expedite this because Manchester is starting to teach this very soon.

Still happy to have conversations around the small details of this PR. But lets follow those up in smaller conversations.