Move betafeatures images into the images dir.

It's not really nice to have this lying around in the root of the
extension. Even if it's for beta, better to use a proper subdir, so the
directory is somewhat 'readable'

Change-Id: Ib6e6b27b2169626a4f9028fa0f772bbdab16a40c

Math.hooks.php

@@ -162,7 +162,7 @@ class MathHooks {
 				'label-message' => 'math-preference-mwmathinspector-label',
 				'desc-message' => 'math-preference-mwmathinspector-description',
 				'screenshot' => $wgExtensionAssetsPath .
-					"/Math/betafeatures-icon-VisualEditor-formulae-$dir.svg",
+					"/Math/images/betafeatures-icon-VisualEditor-formulae-$dir.svg",
 				'info-message' => 'math-preference-mwmathinspector-info-link',
 				'discussion-message' => 'math-preference-mwmathinspector-info-link',
 				'requirements' => array(