Make MySQL configuration files/docs consistent

- use petclinic as the db name and root password

Fixes #322

src/main/resources/application-mysql.properties

@@ -1,7 +1,7 @@
 # database init, supports mysql too
 database=mysql
-spring.datasource.url=jdbc:mysql://localhost/test
+spring.datasource.url=jdbc:mysql://localhost/petclinic
 spring.datasource.username=root
-spring.datasource.password=root
+spring.datasource.password=petclinic
 # Uncomment this the first time the app runs
 # spring.datasource.initialization-mode=always