[checkstyle] editorconfig = easy style conformance

More info at http://editorconfig.org - this makes it easy for editors to
automatically perform the right indentation.

.editorconfig

+# For more info, see: http://EditorConfig.org
+root = true
+
+[*.java]
+indent_style = space
+indent_size = 2
+
+[*.md]
+indent_style = space
+indent_size = 2
+
+[*.xml]
+indent_style = space
+indent_size = 2