Put definition of constant values on cpp file
Add skeleton of RdInputLib

Add skeleton of RdInputManager and all the related classes, but
without the implementation of the key functions.
Add basic support for keyboard input events

Add support for keyboard input events for a basic set of
printable characters: [0-9][a-z].
Add support for non-printable keys to RdKey

Add support for control keys such as ESCAPE, BACKSPACE,
or ARROWS.