INT-2496 GemFire Schema Documentation

Fix Gemfire schema to eliminate reference to a file adapter. Added schemadoc for error-channel while at it

spring-integration-gemfire/src/main/resources/org/springframework/integration/gemfire/config/xml/spring-integration-gemfire-2.1.xsd

@@ -129,9 +129,8 @@
 			<xsd:annotation>
 				<xsd:documentation>
 					Configures an outbound Channel Adapter that
-					writes Message payloads to a
-					File.
-                </xsd:documentation>
+					writes Message to a Gemfire cache
+				</xsd:documentation>
 			</xsd:annotation>
 			<xsd:sequence>
 				<xsd:element name="cache-entries" type="beans:mapType"
@@ -140,7 +139,7 @@
 						<xsd:documentation>
 							A map of SpEL expressions used to create cache entries. If not
 							provided, payload must be a Map
-                	</xsd:documentation>
+					</xsd:documentation>
 					</xsd:annotation>
 				</xsd:element>
 			</xsd:sequence>
@@ -198,6 +197,12 @@
 			<xsd:annotation>
 				<xsd:appinfo>
 					<tool:annotation kind="ref">
+						<xsd:documentation><![CDATA[
+							Identifies the channel to which error messages will be sent if a failure occurs in this
+							component's invocation. If no "error-channel" reference is provided, this component will
+							propagate Exceptions to the caller. To completely suppress Exceptions, provide a
+							reference to the "nullChannel" here.
+						]]></xsd:documentation>
 						<tool:expected-type
 							type="org.springframework.integration.MessageChannel" />
 					</tool:annotation>