Fix #1797: added IconSize option to export extension.

src/extensions/export/bootstrap-table-export.js

@@ -48,7 +48,9 @@
             if (!$export.length) {
                 $export = $([
                     '<div class="export btn-group">',
-                        '<button class="btn btn-default dropdown-toggle" ' +
+                        '<button class="btn btn-default' +
+                            sprintf(' btn-%s', this.options.iconSize) +
+                            ' dropdown-toggle" ' +
                             'data-toggle="dropdown" type="button">',
                             sprintf('<i class="%s %s"></i> ', this.options.iconsPrefix, this.options.icons.export),
                             '<span class="caret"></span>',