[IDE][Enhancement] Add common usings by default when adding a new class

[blat-blatnik]

When I add a new class to a project, the compiler currently inserts some boilerplate code in the new file:

namespace $(ProjectName)
{
	class $(ClassName)
	{
	}
}

But then I always have to go and add using System; using System.Collections; using System.IO; at the top. I think this is common enough that these should be included in the template:

using System;
using System.IO;
using System.Collections;

namespace $(ProjectName)
{
	class $(ClassName)
	{
	}
}

That will save a few keystrokes every time.