Fixed synopsis typo
Bio::SeqIO::new POD update
Mention -string parameter in POD
More POD clarifications
Removed mentions the ARGV and STDIN features

1/ their documentation was less than clear
2/ they seem to have been broken for quite some time
3/ tests disagree that STDIN should be used this way
Fixed missing detection of format in SeqIO when given a -string
Slight SeqIO::guess code flow change
Added autodetection of file format in Bio::SeqIO::MultiFile
Finished variable rename