Fix set state calls

This branch consists of several changes to this.setState calls. This could allow us to use PureComponent instead of Component which could result in improved performance.

Transformations include:

• this.setState(prevState => {return {...}}) ➡ this.setState(prevState => ({...}))
• Better ts types for setState related methods (using keyof Something instead of string) - increases type safety and prevents typos.
• Using functional logic in react setState closures which is preferred in general (I would suggesting updating typescript so that setState callbacks can benefit of optional chaining i.e. prevState?.sections.map(a => ...) instead of prevState.sections ? prevState.sections.map(a => ...) : undefined)
• Removing unused parameters