Add post section : Create manifest and icons directories for read-only applications if they are missing

BUG=https://crosswalk-project.org/jira/browse/XWALK-1208

Signed-off-by: Baptiste DURAND <baptiste.durand@open.eurogiciel.org>
Merge pull request #1718 from eurogiciel-oss/dev_baillaw

 Add post section : Create manifest and icons directories for read-only applications if they are missing