Loading script CSS update

[Maksims]

I've looked at loading.js (default loading script), and it hasn't been updated for very long time now. Few things that can be improved:

• [x] Better way to write CSS.
• [x] Reading flow (order) of things, for other developers to modify it better.
• [ ] Loading bar needs some constant animation, to assist long loading assets, so they don't look like stuck loading for them.
• [ ] Error handling during loading. Right now if it fails to load/run, nothing happens.

[willeastcott]

I'm not sure that loading bar is a visual improvement (although it probably does help people believe loading is still continuing). I've assigned this to @rawkas since I think this could benefit from a designer's opinion.

[willeastcott]

Maybe this suggestion could be 2 part. Part 1: Refactor CSS. Part 2: Change styling.

[willeastcott]

I've just implemented 1 and 2.