Use source 1.7 until eclipse supports JDK 8

Specifically set the source level in generated eclipse projects to 1.7
rather than 1.8. Allows the current eclipse milestone (4.3 M6) in
combination with JDK 8.0 to be used for Spring 4.0 development.

gradle/ide.gradle

@@ -5,6 +5,12 @@ import org.gradle.plugins.ide.eclipse.model.SourceFolder
 apply plugin: "propdeps-eclipse"
 apply plugin: "propdeps-idea"
 
+// Until eclipse fully supports Java 8 use 1.7 source level
+eclipse.jdt {
+	sourceCompatibility = 1.7
+	targetCompatibility = 1.7
+}
+
 // Replace classpath entries with project dependencies (GRADLE-1116)
 eclipse.classpath.file.whenMerged { classpath ->
 	def regexp = /.*?\/([^\/]+)\/build\/[^\/]+\/(?:main|test)/ // only match those that end in main or test (avoids removing necessary entries like build/classes/jaxb)