merge: refactor use of curses

Tidy:
 * eliminate curses from Progress Bar
 * move colour definitions to color.h
 * tidy naming of color functions
 * move KeyEvent out of mutt_curses.h

Refactor:
 * SET_COLOR() to mutt_curses_set_color()
 * NORMAL_COLOR() to mutt_curses_set_color()
 * ATTR_SET() to mutt_curses_set_attr()
 * curs_set() to mutt_curses_set_cursor()
 * beep() to mutt_beep()
 * addch() to mutt_window_addch()
 * addnstr() to mutt_window_addnstr()
 * addstr() to mutt_window_addstr()
 * clrtobot() to mutt_window_clrtobot()
 * move() to mutt_window_move_abs()
 * printw() to mutt_window_printf()
 * mutt_window_mvaddstr()
 * clearok() to mutt_window_clear_screen()
 * mutt_window_getxy() to mutt_window_get_coords()