Some storages need to use different calls for deleting files or folders,
usually unlink() and rmdir().

Fixes #4532 (SMB dir deletion)
Fixes #5941 (FTP dir deletion)

Note that the extra is_dir() should be fast because it's read from the
stat cache.

- coverage for touch return value
- fixed directory provider to exclude unsupported cases

Now using a different content to make sure the file was overwritten.

Also fixed "rename" unit test that was ready the result out of the wrong
file.

When accessing a shared folder, the folder's owner appears as mountpoint
but wasn't wrapped by a quota storage wrapper.

This fix makes sure that all home storages are wrapped by a quota
storage wrapper, if applicable, to make sure quotas are respected when
uploading into shared folders.

Since unlink() smb4php doesn't return true on deletion success, we need
to check whether the file was deleted to confirm success.

Fixes #5866

Fixes #4593

Added argument to getFileInfo() to disable adding the size of
mountpoints to a directory's size.

Fixes #5924

Now removing "/./" and trailing "/." from the paths when normalizing.

Legacy home storage ids with the format "local://path/to/datadir/user1"
are now also wrapped by the HomeStorage.

Add a table with a numeric column and an empty default directive.

Added clearstatcache to make sure we get the correct file size after
re-writing into the same file.

This failed on openSUSE 12.3 x86_64