apps/nsq_to_file: supported rotate by size & interval, added <PID> format tag 


apps/nsq_to_file: supported rotate by size & interval
    
ADD:
--rotate-size=0,        rotate the file when it grow bigger than `rotate-size` bytes
--rotate-interval=0,    rotate the file every duration

CHANGE:
1. rename <GZIPREV> to <REV> in filename format for the new featrue
2. `Sync` before `Close`
3. deprecate `maxGzipRevisions`

apps/nsq_to_file: add <PID> filename format tag