Merge pull request #1 from MahApps/master

Rebase master
Fixed TextBox watermark alignment

MetroTextBox and SearchMetroTextBox styles:
1. Added template binding for watermark horizontal alignment.
2. Changed watermark margins for better look when vertical alignment
active.

MetroDemo:
1. Added some TextBoxes and ToolTips to show horizontal alignments.
2. Removed unnecessary vertical alignments.
3. Make equal appearance for headers in text tab (capital B in TextBox,
PasswordBox as was in RichTextBox).
Removed 60 px limitation
Included 20px MinHeight and MinWidth
Merge pull request #604 from CraftVersum/progress-ring-size

Support for smaller ProgressRings
Demo: Added different ProgressRing sizes
Merge pull request #605 from zii-dmg/master

Fixed TextBox watermark alignment