Implemented styling overrides based on active size

[miguelocarvajal]

This PR lets us set styling based on the grid's active size. Similar to how you can set smSize, lgSize, etc. now you can do smStyle, lgStyle.

This is pretty cool cause now I can control padding and margins based on the layout.

[miguelocarvajal]

Do you need me to do anything to this PR in order to incorporate it into the master?

[srolija]

Is there specific case for which this is change is required?
As far as I remember, it used to be like that, but we changed it before releasing 1.0, because:

1. justifyContent: 'flex-start' is the default so there is no need to override it
2. alignItems: 'stretch' is the default so we need to override it to prevent elements without specific size from stretching by default (which can still be achieved with <Block size="stretch">)

[miguelocarvajal]

I don't remember why off the top of my head, I think it had something to do with react-native-web. I'll try to do some tests before the end of next week and will let you know!

[srolija]

Thank you for updating to work with the latest version, this should make it much easier to merge.

I am really sorry that I haven't replied before, the everyday job got in the way and then I completely forgot about it. I hope to review this PR once again and merge it when I get a bit more time by the end of this week. I have already planned next week to work through a few other issues so the plan would be to fix all of them and release new versions by the end of next week.

[miguelocarvajal]

Is there anything else you need me to do to merge this PR?

Let me know!