Update README.md

Added ResizeGrip with DragSupport to

- MetroWindow and
- SimpleMetroWindow

Automatic ResizeGrip (with drag & drop) support is also available in StatusBar added to either window.

Bugfix on background color in scrollviewer (bottom right corner and o…

…ther elements where transparent)

Added additional methods in IAppearanceManager and IThemeInfos to sup…

…port additional use cases for defining themes from scratch.

Merge branch 'master' of https://github.com/Dirkster99/MLib

BugFixed HorizontalContentAlignment, VerticalContentAlignment in Tree…

…ViewItem to not produce error message (but apply default instead) if binding to ItemsControl cannot be realized.

Added ProgressBar ControlTemplate to also support using non-Metro pro…

…gressbars via ProgressStyleKey

Small bugfix on highlighting of inactive selected treeview item

Added SetDefaultTheme() method in IAppearanceManager to support custo…

…m definition of default theme.

Increaded version of MDemo to 1.0.5