Removed accent border when unchecked

When unchecked there was always a little bit of the accent border visible, when the element was unchecked, so I added a margin when the element is unchecked.

Also I made the disabled state, better to tell apart from enabled state.
Merge pull request #407 from punker76/master

fix groupbox margin Issue #399
Merge pull request #406 from stefan-schweiger/patch-1

ToggleSwitchButton: Removed accent border when unchecked
Add a event IsOpenChanged to Flyout
TabControl's Headers margin can be set by the user

The TabControl's TabItem's headers can be moved now, while keeping the
margins of the TabControl's same.

http://img560.imageshack.us/img560/8996/54558293.png
TabControl's TabStrip's margin and font size of the TabItem can be set by the user
cleanup of MetroTabItem code for readability
updated release notes
corrected merge issue
added related content files to NET45 project
Basic concept of glow window from GitHub project
Creating a new behavior for a glow and re-organize code.
Clean up demo - set glow brush from XAML.
1. Glow window additional functions.
2. Toolbar - Add margin so that it looks similar to VS.
Another one related to Visibility.
DPI issue
Performance - Run calculation once instead of in the loop.
Math.Ceiling
included files with .NET45 project
minor tweak for MetroWindow