added input function

	input function implemented.
	'i' key in COMMAND_MODE --> change to INPUT_MODE
	'esc' key in INPUT_MODE --> change to COMMAND_MODE
	in INPUT_MODE,
		remember all key inputs, and store it in internal data structure
	set terminal echo in order to printout typed-in char

	cursor calibration.
	when a char is typed in, the cursor also has to move
		(printout-line:col also need to be updated)
	at the end of line, wrap with new line.

Signed-off-by: Seehwan Yoo <seehwan.yoo@dankook.ac.kr>