Fix #860 (external database performance) by using connection pooling … (#864)

* Fix #860 (external database performance) by using connection pooling (using commons-dbcp2)

airsonic-main/src/main/resources/applicationContext-db-embed.xml

@@ -4,11 +4,11 @@
        xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"
        profile="embed">
     <bean id="dataSource"
-          class="org.springframework.jdbc.datasource.DriverManagerDataSource">
+          class="org.apache.commons.dbcp2.BasicDataSource">
 
         <property name="driverClassName" value="${DatabaseConfigEmbedDriver}" />
         <property name="url" value="${DatabaseConfigEmbedUrl}" />
         <property name="username" value="${DatabaseConfigEmbedUsername}" />
         <property name="password" value="${DatabaseConfigEmbedPassword}" />
     </bean>
-</beans>
+</beans>