Use square icon for single-scheme templates

[FWDekker]

At some point during the design, I decided that templates with only a single scheme should have a round icon, just like the scheme. This way, I thought, the user would be able to estimate the complexity of the template from the popup.

However, I suspect that this is confusing, and results in users not understanding the difference between the two types of icons. Therefore, all templates should have square icons, regardless of the number of schemes contained within.