IM3Reader for Perkin-Elmer Nuance

This is a basic reader for the Perkin-Elmer Nuance .im3 format. I don't have access to the file format spec, but I have a fair degree of confidence that the reader works. There isn't much in terms of metadata extraction.
Overriding the ```close(boolean)``` method to reset all variables should eliminate the need to override ```setId(String)``` (and is strongly recommended in any case).