clingo version 5.0.0

• gringo is no longer released separately, instead it is part of this and upcoming clingo releases
• cleanup of python and lua API (breaks backwards compatibility)
• added new aspif output format replacing the old smodels format
• added input language support for clasp features
  • #edge directives to add acyclicity constraints
  • #project directives for enumeration of projected models
  • #heuristic directives to steer clasp's search
• added theory atoms to write aggregate like constructs
• added stable C API documented with doxygen
• added experimental C++ API based on C API
• added theory propagator interface to clingo APIs
• added support for compilation with Visual Studio 2015
• improved data structures to reduce memory consumption on typical input
• updated to clasp version 3.2.0 + patches