[bean completion proposals] proposals should show up for `this.` prefix

[martinlippert]

Looks like the bean completion proposals do not show up (yet) when there is this. as the prefix:

public class TestBean2 {

    public void foo() {
        this.<*>
    }

}

Would be nice if the bean proposals would show up in this case, too.

[BoykoAlex]

Fixed via 2512212 but needs a unit test.

[BoykoAlex]

Fixed and tested via b47096e