Restructure project directories

Follow the standard of all go projects

cmd/main.go

@@ -0,0 +1,18 @@
+package main
+
+import (
+	"gitlab.com/revalus/grm/internal/grm"
+	"os"
+)
+
+func main() {
+
+	app := grm.GitRepositoryManager{}
+	err := app.Parse(os.Args)
+	if err != nil {
+		os.Exit(2)
+	}
+
+	exitCode := app.Run(os.Stdout)
+	os.Exit(exitCode)
+}