fix help message --local -> --query

Signed-off-by: Andrew Gregory <andrew.gregory.8@gmail.com>
remove unused variable local

Signed-off-by: Andrew Gregory <andrew.gregory.8@gmail.com>
download remote packages

Signed-off-by: Andrew Gregory <andrew.gregory.8@gmail.com>
allow targets to override selected dbs

This makes it easier to include expac in scripts by always loading
targets with enough information to uniquely identify them regardless of
whether --query, --sync, or --file are passed.

Signed-off-by: Andrew Gregory <andrew.gregory.8@gmail.com>
read targets from stdin

Signed-off-by: Andrew Gregory <andrew.gregory.8@gmail.com>