Add ability to override JSR-352 baseContext.xml

While existing functionality provided the ability to override the
components provided in the baseContext.xml (as required for JSR-352
functionality) at a job by job level, this commit allows a user to
specify a base context for all of the JSR-352 based jobs within a JVM.
To set the location of the custom base context, a JVM property
JSR-352-BASE-CONTEXT should be set.

BATCH-2290

spring-batch-core/src/test/resources/META-INF/alternativeJsrBaseContext.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<beans xmlns="http://www.springframework.org/schema/beans"
+	   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	   xsi:schemaLocation="http://www.springframework.org/schema/beans
+                    http://www.springframework.org/schema/beans/spring-beans.xsd">
+
+	<bean id="transactionManager"
+		  class="org.springframework.batch.support.transaction.ResourcelessTransactionManager"/>
+</beans>