Added controller for FileUpload, refactor of main package, try to add forum system.

src/main/java/site/easystartup/web/repo/UserRepo.java

@@ -0,0 +1,8 @@
+package site.easystartup.web.repo;
+
+import org.springframework.data.jpa.repository.JpaRepository;
+import site.easystartup.web.domain.User;
+
+public interface UserRepo extends JpaRepository<User, Long> {
+    User findByUsername(String username);
+}