Add main menu command for "Add new project to existing solution".

data/resources/StringResources.resx

@@ -8003,6 +8003,9 @@ The resources files have been renamed/moved accordingly.</value>
     <value>Open new buffer</value>
   </data>
   <data name="XML.MainMenu.FileMenu.New.Project" xml:space="preserve">
+    <value>&amp;Project...</value>
+  </data>
+  <data name="XML.MainMenu.FileMenu.New.Solution" xml:space="preserve">
     <value>&amp;Solution...</value>
   </data>
   <data name="XML.MainMenu.FileMenu.Open" xml:space="preserve">

src/Main/Base/Project/ICSharpCode.SharpDevelop.addin

@@ -1145,9 +1145,16 @@
 				          shortcut     = "Control|N"
 				          class        = "ICSharpCode.SharpDevelop.Commands.CreateNewFile"/>
 				
+				<Condition name="SolutionOpen" action="Disable">
 					<MenuItem id          = "Project"
 					          label       = "${res:XML.MainMenu.FileMenu.New.Project}"
 					          icon        = "Icons.16x16.NewProjectIcon"
+					          class       = "ICSharpCode.SharpDevelop.Project.Commands.AddNewProjectToSolution"/>
+				</Condition>
+				
+				<MenuItem id          = "Solution"
+				          label       = "${res:XML.MainMenu.FileMenu.New.Solution}"
+				          icon        = "Icons.16x16.SolutionIcon"
 				          shortcut    = "Control|Shift|N"
 				          class       = "ICSharpCode.SharpDevelop.Project.Commands.CreateNewSolution"/>
 			</MenuItem>

src/Main/Base/Project/Src/Gui/Pads/ProjectBrowser/Commands/SolutionNodeCommands.cs

@@ -14,7 +14,9 @@ namespace ICSharpCode.SharpDevelop.Project.Commands
 	{
 		public override void Run()
 		{
-			AbstractProjectBrowserTreeNode node = ProjectBrowserPad.Instance.ProjectBrowserControl.SelectedNode;
+			TreeNode node = ProjectBrowserPad.Instance.ProjectBrowserControl.SelectedNode;
+			while (node != null && !(node is ISolutionFolderNode))
+				node = node.Parent;
 			ISolutionFolderNode solutionFolderNode = node as ISolutionFolderNode;
 			if (node != null) {
 				using (NewProjectDialog npdlg = new NewProjectDialog(false)) {