Remove underscore from WPF event method names

_This issue has forwarded from [Twitter](https://twitter.com/_SoheilAlizadeh/status/1102288334964097027)._
I've created a new .NET Core base WPF with CLI and have got Hello world sample with the following command:
```
dotnet new wpf
```
After that, I've seen the event method for exit from the app, that its name was `ButtonExit_Click`. This issue is for the name convention of WPF event I think it would be nice when we remove the underscore ( _ ) from the method name. This isn't interesting for clean code and we could improve that.
```C#
private void ButtonExit_Click(object sender, RoutedEventArgs e){}

private void ButtonExitClick(object sender, RoutedEventArgs e){}
```
_the sample [repo](https://github.com/devSoheilAlizadeh/WPFIssue)_

/cc @karelz