project: reorganize the structure of the project.

* remove dotnet-tool.json because the project does not rely on any dotnet tools.
* remove Directory.Build.props because the solution has only one project.
* move src/SourceGit to src. It's not needed to put all sources into a subfolder of src since there's only one project.

src/Models/ApplyWhiteSpaceMode.cs

@@ -0,0 +1,16 @@
+namespace SourceGit.Models
+{
+    public class ApplyWhiteSpaceMode
+    {
+        public string Name { get; set; }
+        public string Desc { get; set; }
+        public string Arg { get; set; }
+
+        public ApplyWhiteSpaceMode(string n, string d, string a)
+        {
+            Name = App.Text(n);
+            Desc = App.Text(d);
+            Arg = a;
+        }
+    }
+}