Inline simple selectors used in mapStateToProps

[whymarrh]

As per a discussion with @alextsg and @danjm:

Selectors should be used to abstract "complex" state queries. "Simple" selectors, selectors that simply pull a property from state without any logic, should be inlined into the mapStateToProps function. This is the case for new components (e.g. #4691) and we will need to adjust recently refactored components to fit this style.

Going forward we can (separately) introduce tooling (a custom lint?) to ensure that no logic is put inside mapStateToProps.

[whymarrh]

This isn't an important change