Add a new analyzer and code-fix to detect and recommend when people can use the auto-property pattern.

i.e. if yo have:

```c#
class C {
  int i;
  int P { get { return i; } set { i = value; } }
}
```

It will fade out ```int i;``` and offer to fix the code into:

```c#
class C {
  int P { get; set; }
}
```