SGF-289 - Enumeration restrictions (xsd:enumeration) should be avoided in the XML schema.

Removed the XSD enumeration restriction on the 'type' attribute of the 'index' element definition inside the SDG XML namespace (XSD) allowing the use of property placeholders to specify the Index types on GemFire Cache Region Indexes.

src/test/resources/org/springframework/data/gemfire/config/index-ns.xml

@@ -1,14 +1,22 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <beans xmlns="http://www.springframework.org/schema/beans"
+	   xmlns:context="http://www.springframework.org/schema/context"
 	   xmlns:gfe="http://www.springframework.org/schema/gemfire"
 	   xmlns:util="http://www.springframework.org/schema/util"
 	   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
+		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
 	   	http://www.springframework.org/schema/gemfire http://www.springframework.org/schema/gemfire/spring-gemfire.xsd
 		http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util.xsd
 " default-lazy-init="true">
 
+	<util:properties id="indexConfiguration">
+		<prop key="index.complex.type">HASH</prop>
+	</util:properties>
+
+	<context:property-placeholder properties-ref="indexConfiguration"/>
+
 	<!-- all beans are lazy to allow the same config to be used between multiple tests -->
 	<!-- as there can be only one cache per VM -->
 
@@ -20,8 +28,9 @@
 
 	<gfe:cache properties-ref="gemfireProperties"/>
 
-	<gfe:index id="simple" expression="status" from="/test-index" type="FUNCTIONAL"/>
+	<gfe:index id="simple" expression="status" from="/TestIndexRegion" type="functional"/>
 
-	<gfe:index id="complex" name="complex-index" expression="tsi.name" from="/test-index tsi" type="HASH" imports="import java.util"/>
+	<gfe:index id="complex" name="complex-index" expression="tsi.name" from="/TestIndexRegion tsi"
+			   imports="import java.util" type="${index.complex.type}"/>
 
 </beans>