add banner and remove unused class

src/main/resources/banner.txt

@@ -0,0 +1,6 @@
+ ____ _____ ___ ____  _     ___ _   _  ____       ____  ____  _____ 
+/ ___|_   _|_ _|  _ \| |   |_ _| \ | |/ ___|     |  _ \|  _ \|  ___|
+\___ \ | |  | || |_) | |    | ||  \| | |  _ _____| |_) | | | | |_   
+ ___) || |  | ||  _ <| |___ | || |\  | |_| |_____|  __/| |_| |  _|  
+|____/ |_| |___|_| \_\_____|___|_| \_|\____|     |_|   |____/|_|                                                                 
+Powered by Spring Boot ${spring-boot.version}