Second Draft: Turn properties into first class accessors

[Richard (Rikki) Andrew Cattermole]

There is a guarantee that I want for this.

The compiler will guarantee that for every assignment that has a paired 
read, that there will be no other reads.

```d
@property {
     int value();
     void value(int);
}
```

```d
value += 2 + value;
```

Would be:

```d
{
     int __generatedName = value;
     value(__generatedName + 2 + __generatedName);
}
```

Not:

```d
value(value + 2 + value);
```

Furthermore, the loaded value must not escape the load statement.

This may seem unnecessary, but without this, I cannot think of a way for 
escape analysis to work with it.

With these guarantees, we might be able to special case it just enough 
for it to be modelable.