By Hongbiao Yang
  Changes to be committed:
	modified:   commands.c
	modified:   commands.h
Bug fix:
	1) Fix the bug of command "tree", display only current directory,
	   and files infomation are also displayed
	2) Fix the bug of command "status", add more infor of the command
	3) Fix the bug of command "open", allow "wr" and "rw" for flag,
	   also the offset is by default 0 instead of end of the file when
	   write.
Merge branch 'master' of https://github.com/Mkvsshine/SimUnixFS