Introduce database-name in <jdbc:embedded-database>

Prior to this commit, the EmbeddedDatabaseBeanDefinitionParser set the
name of the embedded database that it configured to the value of its
'id'. This made it impossible to assign unique names to embedded
databases if the same bean 'id' (e.g, 'dataSource') was used across
multiple application contexts loaded within the same JVM, which is
often the case within an integration test suite. In contrast, the
EmbeddedDatabaseBuilder already provides support for setting the name
in Java Config. Thus there is a disconnect between XML and Java
configuration.

This commit addresses this issue by introducing a 'database-name'
attribute in <jdbc:embedded-database />. This allows developers to set
unique names for embedded databases -- for example, via a SpEL
expression or a property placeholder that is influenced by the current
active bean definition profiles.

Issue: SPR-12835

spring-jdbc/src/main/resources/org/springframework/jdbc/config/spring-jdbc-4.2.xsd

@@ -34,6 +34,16 @@
 							</xsd:annotation>
 						</xsd:element>
 					</xsd:sequence>
+					<xsd:attribute name="database-name" type="xsd:string" default="">
+						<xsd:annotation>
+							<xsd:documentation><![CDATA[
+			The name to assign to the embedded database. Note that this is not the
+			bean name but rather the name of the embedded database as used in the JDBC
+			connection URL for the database. Defaults to "testdb" if an explicit bean
+			'id' has not been provided.
+							]]></xsd:documentation>
+						</xsd:annotation>
+					</xsd:attribute>
 					<xsd:attribute name="type" type="databaseType" default="HSQL">
 						<xsd:annotation>
 							<xsd:documentation><![CDATA[