Added more Icons: 1256

- appbar_calendar_plus
Can now specify animation options when showing/hiding custom in-window metro dialogs
Eliminated the need to pass the owning BaseMetroTabControl to MetroTabItem
removed superfluous property OwningTabControl from MetroTabItem
updated migration guide
using TreeHelper.TryFindParent
removed obsolete c'tor
don't know where this using came statement from...
Merge pull request #1624 from thoemmi/MetroTabItem-without-OwningTabControl

Eliminated the need to pass the owning BaseMetroTabControl to MetroTabItem
Update 1.0.0.md
Code cleanup
introduced Flyout.ClosingFinished event
added dynamic fylout to demo
hide Flyout even w/o HideStoryboard
refactored handling of closing flyouts
use the best matching icon frame
showing again before hiding has finished may result in invisible flyout
minor casing
Merge pull request #1626 from thoemmi/Flyout-CloseFinished

added event `ClosingFinished` to `Flyout`
Merge pull request #1628 from thoemmi/icon-size-fix-1242

Use correct size for window icon