Cleaned up codef or a few files

Cleanup up the following files.  I figured I would only do a few at a time.

- Used var where applicable.
- Fixed invalid spacing.
- Inverted if statements to reduce nesting.
- Changed multiple if statement to switches.
- Fixed misspelled words in comments.

MahApps.Metro\Controls\RangeSlider.cs
MahApps.Metro\Controls\RevealImage.xaml.cs
MahApps.Metro\Controls\ScrollViewerOffsetMediator.cs
MahApps.Metro\Controls\SplitButton.cs
MahApps.Metro\Controls\TextboxHelper.cs
MahApps.Metro\Controls\Tile.cs
MahApps.Metro\Controls\ToggleSwitch.cs
MahApps.Metro\Controls\TransitioningContentControl.cs
MahApps.Metro\Controls\TreeHelper.cs
MahApps.Metro\Controls\WindowSettings.cs
MahApps.Metro\ThemeManager.cs