fix bug like {c:Binding .} and add support for shortcut of RelativeSource

[endlesstravel]

see issue #72

it will lead {c:Binding .} work like {Binding .}

[endlesstravel]

add support for shortcut of RelativeSource at 85ca73b

zzzzz@PreviousData           // means {Binding Path=zzzzz, RelativeSource={RelativeSource PreviousData}}
yyyyy@TemplatedParent        // means {Binding Path=yyyyy, RelativeSource={RelativeSource TemplatedParent}}
Parent.Name@Self             // means {Binding Path=Parent.Name, RelativeSource={RelativeSource Self}}
xxxx@FindAncestor.Grid       // means {Binding Path=xxxx, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Grid}}}
xxxx@FindAncestor[2].Grid    // means {Binding Path=xxxx, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Grid}, AncestorLevel=2}}
xxxx@Grid                    // means {Binding Path=xxxx, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Grid}}}
Title@Window                 // means {Binding Path=Title, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}}