Add proper handling of overwriting read-only destination files

When overwriting destination files, CH uses the "Protect read-only files" setting to determine if it needs to change the attribute before overwriting file. In case the option is on, then there is no possibility to overwrite the file. On the other hand, when the option is off, CH almost always try to change the attributes of destination file before writing into it. That's not very efficient.

Change that behavior so that user is informed via feedback dialog that the file is read-only and give him the option to overwrite the file (which will change the attributes then). That would also give the option to remember the feedback response also for other read-only files.