set task limit
add record monitor call back & small modifications
- record monitor: check if record is data
- modifications: collector should have unlimited scheduling cycle,
  default: unlimited scheduling cycle
allow user to set negative demand limit
  - use flag -nd <num>
Merge branch 'master' of https://github.com/snetdev/snet-rts
- remove redundant variable & update LPEL_FLAGS
 + dloc_placement is removed as it is not used in LPEL_HRC
Merge pull request #49 from nguyenvuthiennga/master

small modifications & add user-defined option in LPEL HRC