Make recursive push work.

This introduces a path normalization helper that turns filenames
into entity IDs where needed to allow the push of a directory
to the device to work.
Fix C++ comment.
Fix hopelessly short timeout in file transfers.

The client code was using the default 25 second timeout for
file transfer operations, which is far too short.
Add display name support to gvfs-ls.
Ubuntu: Shared libgvfscommon