Converted QTFormat

Converted the LegacyQTReader/Writer and NativeQTReader/Writer from
loci.formats to LegacyQTFormat and NativeQTFormat, respectively, in
ome.scifio.formats.

Removed the DelegateReader class, instead adding an enabled/disabled
logic to the Format interface.

The NativeQTFormat has a higher priority than LegacyQTFormat so it will
always be chosen first. To switch to LegacyQTFormat, simply disable the
NativeQTFormat.
Converted NRRDFormat

Converted the loci.formats NRRDReader to an ome.scifio NRRDFormat.
Converted PICTFormat

Converted the loci.formats PictReader to an ome.scifio PICTFormat.