fix bug of schedular error on workers
update circuit description
add Check flow to master and worker
apply flow path on Master/Config and Worker/Config
add check() to Schedular module
move config procedure to the startup
add comment in schedular.js
simplify codes
update example section in README
move main flows from 'flow' dir to 'main'
remove Config/* flows
load flow by path list in schedular module
justify codes to the changes of path list in the schedular module
add lib/extra/ dir for extra flows
add HttpServer/* to the extra flows
fix presentation on receiving signals in Master/Start flow
update main flows as the removal of fid in the arsenal.Pipeline mechanism
make HttpServer/* flow configurable
add exception catcher in Worker/Load flow
use WARNING level for logging in Worker/Load and Worker/Unload flows