[WIP] use validation error template and fix some issues

- [x] create a ValidationErrorTemplate
- [x] repositioning if host-window size or location changed
- [x] repositioning if host-window gets maximized and vice versa
- [x] new custom popup control only topmost if the host-window is activated

there is a bug in wpf adorner system, so all controls with validation in tabitems must be hosted in a AdornerDecorator.

- [x] use ValidationErrorTemplate at TextBox
- [ ] use ValidationErrorTemplate at ButtonCommandMetroTextBox
- [ ] use ValidationErrorTemplate at CheckBox
- [ ] use ValidationErrorTemplate at ComboBox
- [ ] use ValidationErrorTemplate at DatePicker
- [ ] use ValidationErrorTemplate at PasswordBox
- [ ] use ValidationErrorTemplate at RadioButton

Closes
#589 
#682 
#71