[RFC] clear type stuff

ClearType partially not working, so this pr should fix some of it

- [x] ```TextBox``` ignores ClearType
- [x] ```ComboBox``` and ```Menu``` popup ignores ClearType
  - [x] fix ComboBox ClearType
  - [x] set the correct ```Effect``` to enable ClearType (for ComboBox)
  - [x] fix Menu ClearType
  - [x] maybe another Controls too

Benefit
- we got a ClearType enabled ui

Side effect
- if we set ```AllowTransparency="False"``` for popups, we lost the popup animation, so **don't** do it :-D

**Guidlines**, if the user wants clearer text
- inherite from default style and add this lines
```xml
    <Style TargetType="ComboBoxItem"
           BasedOn="{StaticResource MetroComboBoxItem}"
           x:Key="ClearMetroComboBoxItem">
        <Setter Property="TextOptions.TextRenderingMode"
                Value="ClearType" />
        <Setter Property="TextOptions.TextFormattingMode"
                Value="Display" />
    </Style>
```
| **Scenarios** | **Recommended Mode** |
| --- | --- |
| Large Text (15pt+) | Ideal \ Display (users preference) |
| Transformed Text | Ideal |
| Zoomed Text | Ideal |
| Design Scenarios | Ideal |
| Small Text | Display |

Closes #1536