~ Move UI to new FileSyncDialog class;
~ Improve UI responsiveness during operation (closes#5005);
+ Add log verbosity option (also helps with UI response);
+ Add several filtering settings in new "extra options" panel (include/exlude patterns, symlinks, recursive, empty folders);
~ Exclude patterns ".*" and "System Volume*" by default (addresses #5213, #5106);
+ Sanity check file timestamps when using date comparison, future dates are invalid (addresses #5735);
~ Folders are no longer included in file counts (total/created/etc);
~ Ignore unreadable files/dirs (also enables NTFS permissions check);
~ Switch from QMutex to QReadWriteLock.
