Fix inconsistencies between old and new file transfers methods.

[diederik]

Currently there are some inconsistencies between FileTransfer and FileTransferP2P. For example:

• old file transfers don't honor the "useReceivedFilesDir" setting.
• old file transfers never display previews (use KMimeType::iconNameForUrl for that).
• Some chat notification messages are broken, ie the filename isn't displayed or is displayed differently than with P2P transfers: Sending file software.tar.bz2 ...or..The transfer of software.tar.bz2(I18N_ARGUMENT_MISSING) has failed. Unable to establish a connection. (retranslated back from Italian, the wording may be different, but I kept text formatting)
• When accepting a file, the save as dialog doesn't show the entire suggested filename, but the extension only
• maybe something more as well...

[valerio]

This has been fixed with revision r3671.