WriteBytestream::write(…) now returns a boolean indicating its success state (false in case of an error). Adjusted FileWriteBytestream accordingly. The QtWebKitChatView will test if the file path selected by the user is writable before accepting it and starting the transfer. If it is not writable a red warning message will be added to the file-transfer element in the chat view. Test-Information: Added an integration test that tests the new behavior for the FileWriteBytestream class. Tested two file transfers on OS X 10.11.3, one to a write protected location and another to /tmp. The first is not accepted by the UI, and without the UI sanity check it results in a file-transfer error. The second succeeds as expected. Change-Id: I5aa0c617423073feb371365a23a294c149c88036