Just a minimal code reduction, but big reduction in code
duplication. This could help if in the future, support for
different "internationalization" mods will be added, or in
case Minetest supports I18N/L10N internally in the engine.
into two files - one with the nodebox models, and one with the
actual node definitions.
In the process, cleaned up the code that handles node_ownership
and protection mods.
Also made the mod automatically enable either left-click or right-click to
open/close a door, depending on whether the game supports it (actually it
checks for the existance of an unrelated function that happened to be added at
the same time as the new right-click function).
Renamed some textures, duplicated all of the _lr.png textures to make it
easier to register the textures in a loop and to allow for more flexible
texturing.
