Added samples for addch, attron, mouse tracking and colors

[coezbek]

Additional samples which demonstrate various functions of curses:

• addch: How to add styled characters.
• colors: How to test if colors are supported and print them.
• mouse_move: How to capture mouse move events and enable CSI mode.
• attr_demo: Sample which shows each standard style.

[shugo]

Thanks for your contribution!