Update install.sh, add line-types/color to shell.

Add:
	install.sh
		-add documentation header comment, and command to install ncurses.

	makefile
		-set default profile for the gnome-terminal containing the engine's
		shell.

	src/interpreter/shell_graphics.c
		-add color initialization to configureShell().
		-add VisualLine_t typdef'd struct, and line type value macros to allow
		for lines with different colors (eg, an arguments line printed in cyan
		and an error message printed in red).
		-change prompt to empty string for non-command lines.