Log Message:
Update contao41 to 4.1.3.

### 4.1.3 (2016-04-22)

 * Use data URIs for the image preview in the back end.
 * Use DIRECTORY_SEPARATOR to convert kernel.cache_dir into a relative path (see \ 
#464).
 * Always trigger the "isVisibleElement" hook (see contao/core#8312).
 * Do not change all sessions when switching users (see contao/core#8158).
 * Do not allow to close fieldsets with empty required fields (see contao/core#8300).
 * Make the path related properties of the File class binary-safe (see \ 
contao/core#8295).
 * Correctly validate and decode IDNA e-mail addresses (see contao/core#8306).
 * Skip forward pages entirely in the book navigation module (see contao/core#5074).
 * Do not add the X-Priority header in the Email class (see contao/core#8298).
 * Determine the search index checksum in a more reliable way (see contao/core#7652).