Add support for compound parameters

[Richiban]

Parameters to methods should be able to be compound types (possibly tagged with at attribute?).

E.g. instead of

[CommandLine]
public void M(string p1, string p2)
{
	...
}

We should be able to write something like:

class Params
{
	public string P1 { get; set; }
	public string P2 { get; set; }
}

[CommandLine]
public void M([CompoundParameter] Params params)
{
	...
}