Fix sorting by date

Problem:

After installing Cakebox, the sort by date doesn't work like expected.
There is no sort on files create after the installation of Cakebox.
Cakebox use getCTime on the controller Directory to get the last modification of a file.
getCtime() only get the inode change time of the current DirectoryIteraor item.

Fix:

We now use getMtime() to get the last modification of the current file.
Merge branch 'master' of https://github.com/Cakebox/Cakebox-light

Conflicts:
	app/controllers/directories.php