Use new FileUtils methods for in the client.

Change-Id: I8dd7ba2f57c43ca64d7ea978a34e00749396a035
Depends-On: I20d3a7b908bbeae833ffffe0598b99bde47021c7
Reviewed-on: http://gerrit.dmdirc.com/4074
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Chris Smith <chris@dmdirc.com>