Update JNA to 3.2.4

Signed-off-by: Jussi Virtanen <jussi.virtanen@valotrading.com>
Convert NCurses to abstract class

Signed-off-by: Jussi Virtanen <jussi.virtanen@valotrading.com>
Remove NCursesLibrary

Move the native methods from NCursesLibrary to NCurses. This simplifies
the use of the library as the user needs to interact with only one API.

Signed-off-by: Jussi Virtanen <jussi.virtanen@valotrading.com>
Merge pull request #14 from jvirtanen/features/direct-mapping

Use JNA's direct mapping technique