Bump Cesium version to b18.

Author: mramato

build.xml

@@ -109,7 +109,7 @@
 
 	<!-- Inputs -->
 	<!-- this version should be set to the upcoming version, so it can be tagged without requiring a bump first -->
-	<property name="version" value="b17" />
+	<property name="version" value="b18" />
 	<property name="sourceDirectory" location="Source" />
 	<property name="shadersDirectory" location="${sourceDirectory}/Shaders" />
 	<property name="examplesDirectory" location="Examples" />