Added some documentation about the coming VFS.

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+The VFS in T/CE :
+
+File are objects that implement an abstract file class in the kernel. Its methods are :
+- int open(process *pr, int mode)
+- void close(process *pr)
+- int read(size_t offset, size_t len, char *buffer)
+- int write(size_t offset, size_t len, char *buffer)
+- int stat(struct file_info *info)
+- file* get_child(char* name)
+- int add_child(char* name, file *child)
+
+The following syscall interface is given to the process (fd_t is a file descriptor, an int) :
+- fd_t open(char* filename, int mode)
+- fd_t open_relative(fd_t root, char* filename, int mode)
+- int stat(char* filename, struct file_info *info)
+- int statf(fd_t file, struct file_info *info)
+- void close(fd_t file)
+- int read(fd_t file, size_t offset, size_t len, char *buffer)
+- int write(fd_t file, size_t offset, size_t len, char *buffer)
+- int link(char *from, char *to, int mode)
+
+struct file_info {
+	int type
+	int dev_type
+	int mode
+	int uid, gid
+	int size
+}
+
+File open modes flags :
+- FM_READ		open for reading
+- FM_WRITE		open for writing
+- FM_APPEND		append data
+- FM_TRUNC		truncate existing file
+- FM_CREATE		create file if it doesn't exist
+note : if mode contains neither FM_READ nor FM_WRITE, then the file will be created/truncated according to the flags given,
+	but will not be actually oppenned, so the return value of open will be 0.
+
+Link modes :
+- LM_SYMLINK
+- LM_HARDLINK	(don't count on that really being implemented)
+- LM_MOUNT
+- LM_OUTPUT_TO	(keyboard outputs to virtual terminal, virtual terminal outputs to display, that kind of stuff.)
+
+File type flags :
+- FT_FILE
+- FT_DIR			// block devices that contain a partition table will have this flag
+- FT_SYMLINK
+- FT_DEV			// any kind of device with special properties (keyboard, hdd, disk partition, ...)
+- FT_TERMINAL		// virtual terminal
+
+Device types :
+- DT_BLOCK
+- DT_KEYBOARD
+- DT_DISPLAY