Moved application code to the Application layer

Imported Win10 project
Code cleanup
WIP - Use common UWP services for Win8.1 and Win10

ModernKeePass10/Common/RelayCommand.cs

@@ -0,0 +1,78 @@
+using System;
+using System.Windows.Input;
+
+namespace ModernKeePass.Common
+{
+    /// <summary>
+    /// A command whose sole purpose is to relay its functionality 
+    /// to other objects by invoking delegates. 
+    /// The default return value for the CanExecute method is 'true'.
+    /// <see cref="RaiseCanExecuteChanged"/> needs to be called whenever
+    /// <see cref="CanExecute"/> is expected to return a different value.
+    /// </summary>
+    public class RelayCommand : ICommand
+    {
+        private readonly Action _execute;
+        private readonly Func<bool> _canExecute;
+
+        /// <summary>
+        /// Raised when RaiseCanExecuteChanged is called.
+        /// </summary>
+        public event EventHandler CanExecuteChanged;
+
+        /// <summary>
+        /// Creates a new command that can always execute.
+        /// </summary>
+        /// <param name="execute">The execution logic.</param>
+        public RelayCommand(Action execute)
+            : this(execute, null)
+        {
+        }
+
+        /// <summary>
+        /// Creates a new command.
+        /// </summary>
+        /// <param name="execute">The execution logic.</param>
+        /// <param name="canExecute">The execution status logic.</param>
+        public RelayCommand(Action execute, Func<bool> canExecute)
+        {
+            if (execute == null)
+                throw new ArgumentNullException(nameof(execute));
+            _execute = execute;
+            _canExecute = canExecute;
+        }
+
+        /// <summary>
+        /// Determines whether this <see cref="RelayCommand"/> can execute in its current state.
+        /// </summary>
+        /// <param name="parameter">
+        /// Data used by the command. If the command does not require data to be passed, this object can be set to null.
+        /// </param>
+        /// <returns>true if this command can be executed; otherwise, false.</returns>
+        public bool CanExecute(object parameter)
+        {
+            return _canExecute?.Invoke() ?? true;
+        }
+
+        /// <summary>
+        /// Executes the <see cref="RelayCommand"/> on the current command target.
+        /// </summary>
+        /// <param name="parameter">
+        /// Data used by the command. If the command does not require data to be passed, this object can be set to null.
+        /// </param>
+        public void Execute(object parameter)
+        {
+            _execute();
+        }
+
+        /// <summary>
+        /// Method used to raise the <see cref="CanExecuteChanged"/> event
+        /// to indicate that the return value of the <see cref="CanExecute"/>
+        /// method has changed.
+        /// </summary>
+        public void RaiseCanExecuteChanged()
+        {
+            CanExecuteChanged?.Invoke(this, EventArgs.Empty);
+        }
+    }
+}