Log Message:
Update contao43 to 4.3.1, a leaf package.

### 4.3.1 (2016-12-22)

 * Preserve uppercase characters in custom sections IDs (see #639).
 * Always show the section title instead of its ID (see #640).
 * Correctly handle DropZone file uploads (see #637).
 * Fix the markup of the CSV importers (see #645).
 * Correctly symlink the logs directory under Windows (see #634).