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/Commands/CherryPick.cs

@@ -0,0 +1,13 @@
+namespace SourceGit.Commands
+{
+    public class CherryPick : Command
+    {
+        public CherryPick(string repo, string commit, bool noCommit)
+        {
+            var mode = noCommit ? "-n" : "--ff";
+            WorkingDirectory = repo;
+            Context = repo;
+            Args = $"cherry-pick {mode} {commit}";
+        }
+    }
+}