If the file is compressible (i.e. not encrypted or already compressed) it can be marked as such in storageNewRead()/storageNewWrite(). If the file is being read from/written to a remote it will be compressed in transit using gzip.
Simplify filter group handling by having the IoRead/IoWrite objects create the filter group automatically. This removes the need for a lot of NULL checking and has a negligible effect on performance since a filter group needs to be created eventually unless the source file is missing.
Allow filters to be created using a VariantList so filter parameters can be passed to the remote.
This filter exactly mimics the behavior of the Perl filter so is a drop-in replacement.
The filter is not integrated yet since it requires the Perl-to-C storage layer interface coming in a future commit.
Remove "File" and "Driver" from object names so they are shorter and easier to keep consistent.
Also remove the "driver" directory so storage implementations are visible directly under "storage".
Removed the "anchor" parameter because it was never used in any calls in the Perl code so it was just a dead parameter that always defaulted to true.
Contributed by Cynthia Shang.
