Fixed Polish translation loading

The issue described in nokia-developer/rate-my-app#10 was caused by
locale mismatch between demo app (PL) and library (pl-PL). Localization
works if both use pl-PL.
Polish translation file was missing from WP7 XAML

Strange.
WP7 XAML demo leftovers
Updated demo app icons
Latest translations and standard cultures

Included latest version of the translation files and standardized the
cultures according to the list provided by Microsoft at
http://msdn.microsoft.com/en-us/library/windowsphone/develop/hh202918(v=vs.105).aspx
(i.e. "fi-FI" instead of "fi" )
Protected setters for FeedbackHelper's properties

The properties are mean to be set only from inside the component,
therefore their setters are now marked "internal"
Tiny correction to German translation
Added new property VisibilityForDesign to make control visible for designing and developing
Version 1.1 ready for release.
Update README.md
Replaced old version of the doc with new one.

It helps with managing the links from Nokia Developer web site.
Merged latest changes