Map object types are now opaque pointers in the public Map API

Publicly, DMU is a pure C API. Outsiders do not have visibility to
the type or contents of map objects via the pointers used in the Map
API.
Moved map data script and template to the attic

The map data classes will be C++ classes and hand-crafted.
Broke down the generated dd/p_maptypes and reorganized headers
Cleanup
Documentation: Added description for EntityDatabase

Courtesy of danij.
Relocated m_stack to libdeng1

Also spruced up the implementation a little.
Merge branch 'master' into mapdata-c++
Removed the global bspLeafs array

The GameMap is the correct way to access map data.
Removed global bspNodes and hedges arrays

These are not needed any more.
Removed the global lineDefs and sectors arrays

Not needed any more.
Removed global sideDefs, vertexes, and polyObjs arrays

Not needed any more. Now all map data is accessed via GameMap.
Merge branch 'master' into revise-texture-animation

Conflicts:
doomsday/engine/api/dd_maptypes.h
doomsday/engine/include/map/p_maptypes.h
doomsday/engine/include/resource/material.h