LPS-44187 Source Formatting

Hey Nate, 

I've applied the changes you asked for in https://github.com/natecavanaugh/liferay-portal/pull/2157 except for the one about the `_variables.scss` file.

It may seem an overkill now, but otherwise we'll end up with some magic numbers in two different places which could soon turn into a maintenance nightmare. Also, if we have the mechanism already in place, we could reuse it at some point to remove a lot of duplicated variables (colors and so on) that we're currently using. What do you think?

Let me know if you think we can improve this in any other way.

Thanks!

cc @ipeychev