customized & added controls

• added metro style groupbox
• added background highlight color to tabitem headers to match current
theme
fixed groupbox xaml missing from .csproj
Fixed titlebar behavior

https://github.com/MahApps/MahApps.Metro/issues/234
Added support for the "Clear All" button in PasswordBoxes also (not just TextBoxes). Added a dependencyproperty "SelectAllOnFocus".
Added the Gray3 color to both BaseDark.xaml and BaseLight.xaml to make the dropdown arrow in a combobox visible both for the dark and light theme. Added a Title property on the MainWindowViewModel to get rid of databinding error in the MetroDemo project.
Added another gray color to the BaseDark and BaseLight xaml files, for the theme switching during runtime to work.
Fixed arrow colors for the decrement buttons (both horizontal and vertical), they were Gray2 instead of Gray3, which meant they weren't visible using light themes. Also added a missing DisabledElement rectangle.
Merge pull request #259 from zii-dmg/TitlebarFixes

Fixed titlebar behavior
Created a separate branch for bug-fixes:
-The ProgressIndicator now takes into account the Visibility property. It didn't do that before, causing its animation to show even if Visibility is set to Hidden.
-Bumped assembly and nuget version
-Added a ThemeIsDark property on the ThemeManager, so applications can tell which theme is running.
Update readme.md
Update readme.md
Fixed the dotted focus border that shows up on the MetroWindow.
Merge pull request #279 from blooksa/focus_border

Fixed the dotted focus border that shows up on the MetroWindow.
#215 add style for slider with orientation=vertical
Flyout resize fix

When flyouts are dynamically resized, they wont hide properly as they
hide as if they were not resized.
This adds a call to ApplyAnimation on OnRenderSizeChanged which fixes
the issue.
Last panorama column hide fix

I was unable to find a cleaner solution to this, but it doesn't seem to
have any downsides so far.
This fixes an issue where the last column in a Panorama group would
sometimes not be shown.
Fixed the flyout fix

With the previous flyout fix, flyouts would instantly hide when resized,
now they resize properly.
fix RestartTransitionOnContentChange

if the content changes fast, the completed event fires and abort the
transition. this has the effect that the content shows without the new
transition.
Merge branch 'pr/n241_Icehunter'
Merge branch 'pr/n282_punker76'