Added GIFFormat

The loci.formats GIFReader has been converted to an ome.scifio GIFFormat
and components.

The loci.formats reader has been marked deprecated, and now delegates to
the Format.
Added AbstractMetadata#reset comment

Added commented out code to reset ome.scifio.Fields only. We may want to
implement this in the future.
wip: MicromanagerFormat