fixes HOC displayName for observer and inject

[SimeonC]

Uses the convention for HOC display names as outlined in the React documentation.
https://reactjs.org/docs/higher-order-components.html#convention-wrap-the-display-name-for-easy-debugging

Closes #466 <- See for more details.

[mweststrate]

I am not sure about wrapping observer() around non-function components; as for normal components it rather acts as mixing then as HoC. (And I think it will be make the entire component tree probably quite unnecessary very verbose?)

The inject names are definitely better this way.

I marked it as breaking change, as I think it could impact test suites relying on snapshots quite a bit. Not really sure whether that counts as 'breaking' though as there should be no runtime impact. But probably this is best shipped as separate minor at least

[SimeonC]

Yea, it probably is a breaking change for that reason.
My thinking adding the HOC convention to observer was that it would be useful to see which components would be reacting to mobx changes which currently isn't very visible. Didn't think about whether it would be too verbose with it in but it has caught me out every now and then - it also would help to highlight the difference between inject('store') and inject(() => {}) which only one of these applies observer and the other doesn't.

[mweststrate]

Merged into the v6 branch