add pu_cb_progress callback

Signed-off-by: Andrew Gregory <andrew.gregory.8@gmail.com>
pacsync: add event callback with logging

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

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

Signed-off-by: Andrew Gregory <andrew.gregory.8@gmail.com>
add pacsync to program list

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