modify class member name in parser
modify anony_pipe/pipe_manager API, ras add new functionality.

anony_pipe become more OO. pipe_manager become simple.
ras
1. choosing port in CLI argument
2. process childs' output
3. internal command without error handling
add shell init function. read cmd from socket refactor to function.
some bug fix, reorder function prototype in ras.cpp

bug fix
1. dynamic alloc string size should be strlen + 1
2. checking existence of argument before pipe
3. pipe_manager
   - get_pipe should resize vector if pipe doesn't exist
   - create_pipe should set fd_is_closed to false;
modify error output API: use perror() instead of fprintf()+strerror()
add output file redirection
set initial PATH to bin/
modify initial PATH setting and printenv command output
add TA testing file in TA_test dir, replace commands/ dir

using make TA_test to build testing environment of ras shell.
bug fix of stderr output to client. add 2nd type of welcome msg in comment mode.

stderr output fix
1. remove close() after dup2() for simple fd dup to multiple target.
2. add error message for execvp() failed.
update gitignore for TA_test
add failed process checking, which doesn't drive number pipe.