AVIFormat conversion

The loci.formats AVIReader and AVIWriter have been converted to a single
AVIFormat in ome.scifio.formats.

The legacy classes are new delegators, which pass all functionality to
the SCIFIO implementation.

Supporting classes have been copied to SCIFIO (codecs and the
UnsupportedCompressionException) but will be converted to delegators at
a later date.
Removed populateImageMetadata from abstract layer

The empty implementation of populateImageMetadata has been removed from
AbstractMetadata. This is to encourage its implementation with each new
concrete metadata type. This information must always be known, and its
generation will be different for each format, so there is no reason to
have an empty implementation in the abstract layer.
wip: BMPFormat