Can't assign binding to KeyBinding in TextBox 
## 🐛 Bug Report

I have following issue with MVVMCROSS and MethodBinding plugin:

I created new Textbox with assigned keybinding:

    <TextBox>
        <TextBox.InputBindings>
            <KeyBinding mvx:Bi.nd="Command SendToConsole" Key="Enter" />
        </TextBox.InputBindings>
    </TextBox>

And pressing 'Enter' is not executing SendToConsole method. What is more interesting, if I create button with the same command it is working fine:

    <Button mvx:Bi.nd="Command SendToConsole" />

my SendToConsole method looks like this:

    public async Task SendToConsole() 
    {
        // Some code to execute 
    }

But InputBinding is working fine with 

    <TextBox>
        <TextBox.InputBindings>
            <KeyBinding Command="{Binding SendToConsole}" Key="Enter" />
        </TextBox.InputBindings>
    </TextBox>

but I need to change SendToConsole method into public IMvxAsyncCommand SendToPeernetConsole...


**Version:** 6.x

**Platform:** 
- [ ] :iphone: iOS
- [ ] :robot: Android
- [X ] :checkered_flag: WPF
- [ ] :earth_americas: UWP
- [ ] :apple: MacOS
- [ ] :tv: tvOS
- [ ] :monkey: Xamarin.Forms
