Extent the file-system grunt library
Extent the file-system grunt library

New functions available:
- rmdirRecursiveSync to remove a directory and all its content
  synchronously
- copyFile to copy a file asynchronously


Former-commit-id: 728096b23a289de1f2833562eb1c9d82ea4ac636
concrete5/concrete5,olsgreen/concrete5,olsgreen/concrete5,mlocati/concrete5,KorvinSzanto/concrete5,mainio/concrete5,rikzuiderlicht/concrete5,concrete5/concrete5,rikzuiderlicht/concrete5,mainio/concrete5,jaromirdalecky/concrete5,acliss19xx/concrete5,jaromirdalecky/concrete5,a3020/concrete5,jaromirdalecky/concrete5,haeflimi/concrete5,concrete5/concrete5,hissy/concrete5,biplobice/concrete5,jaromirdalecky/concrete5,MrKarlDilkington/concrete5,a3020/concrete5,deek87/concrete5,haeflimi/concrete5,olsgreen/concrete5,triplei/concrete5-8,mainio/concrete5,KorvinSzanto/concrete5,acliss19xx/concrete5,biplobice/concrete5,hissy/concrete5,triplei/concrete5-8,KorvinSzanto/concrete5,haeflimi/concrete5,deek87/concrete5,triplei/concrete5-8,deek87/concrete5,rikzuiderlicht/concrete5,deek87/concrete5,MrKarlDilkington/concrete5,acliss19xx/concrete5,mlocati/concrete5,haeflimi/concrete5,biplobice/concrete5,MrKarlDilkington/concrete5,mlocati/concrete5,mlocati/concrete5,biplobice/concrete5,hissy/concrete5,hissy/concrete5,concrete5/concrete5