Improve Download section

[piotrzarzycki21]

Here is information from Justin's email:

• [x] This button does not download the latest Moonshine release for Mac users. It tries to download the very old App Store version. At a minimum, we should make the Download default for MacOS just be the same as clicking the drop down arrow at the moment until the App Store version is fixed:

• [x] It is really not clear how to get to the Moonshine SDK Installer from Moonshine. The download page for SDK Installer needs to be separate from the main Moonshine download page I think, because the user has to scroll all the way to the lower section to find the SDK Installer.

• [x] We still need a better image here that is at least the width of this, and can be zoomed by clicking on the image. People need to be able to see what Moonshine is at a reasonable level of screen shots before the install it. Really, we should also have a video or presentation... I thought at one point we had that?

[Aszusz]

@piotrzarzycki21 This is ready for approval