WL#3296: Support INFORMATION_SCHEMA.FILES time columns

Implement the "nice to have" columns from WL1359:
 
> CREATION_TIME           As reported by operating system.    
> LAST_UPDATE_TIME        As reported by operating system. 
> LAST_ACCESS_TIME        As reported by operating system. 
> 
>                        For all "as reported by operating system" columns, 
>                        the value may be NULL. But if the implementor 
>                        decides to report it, and the operating system 
>                        supports it, that's nice. 

Involves stat(2) call on all the files on all the nodes. atime probably
inaccurate due to the possibility of disabling atime (mount with noatime).

Good introductory task though (time estimate sort of according to that)