Main changes:
* Change the listing order of files/directories so that the local and remote
snapshots can be compared on-the-fly.
* Introduce a new struct called EntryList that maintains a list of
files/directories, which are kept in memory when the number is lower, and
serialized into a file when there are too many.
* EntryList can also be turned into an on-disk incomplete snapshot quickly,
to support fast-resume on next run.
* ChunkOperator can now download and upload chunks, thus replacing original
ChunkDownloader and ChunkUploader. The new ChunkDownloader is only used
to prefetch chunks during the restore operation.
* Restore/check should report an error instead of a success at the end if there
were any errors and -persist is specified
* Don't compute the file hash before passing the file to the chunk maker; this is
redundant as the chunk maker will produce the file hash
* Add a LOG_WERROR function to switch between LOG_WARN and LOG_ERROR dynamically
You can now add a key 'filters' in the preferences file that points to the
path of the filters file. If this key is not found in the preferences,
the default location '.duplicacy/filters' is used.
There is a new option '-filters' for the set command that set this key in
the preferences, but you can also edit the file directly.
Directories containing a file with this name will not be backed up. I find it easier to drop a .nobackup file in directories I don't want backed up instead of maintaining a file of exclusions. This is also useful for scripts that create data in the repository but don't want it to be backed up.
