kconfig/lxdialog: add a new theme bluetitle which is now default

The bluetitle theme is a slightly modified version of the colorscheme
that -mm users has been used to. The bluetitle is more readable especially
on some LCD screens so it is now default.
Anyone that really wants the old color selection can get it by selecting
the classic color theme:
make MENUCONFIG_COLOR=classic menuconfig

The bluetitle theme was modified by Roman Zippel <zippel@linux-m68k.org>
to further improve readability on LCD screens.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>