Standardizing freeaddrinfo(), close() code flow & exit() return values

exit() argument values changed to be different for every error.
Standardizing the way freeaddrinfo() & close() are called in the code flow.
Added template files for a server & a client
Making using_connect_* files compilable
Adding a basic Makefile.
Makefile made general. All .c will be compiled

Now all the .c files in the listed SRC_DIR will be compiled. No need to add files individually.
Also, seperated rm command for each folder with a new line
A multi user chat server has been added.