Create ABS2PDDL transformation plugin

initiate plugin code for ABS 2 PDDL

also add the initial manual transformation agence.abs -> agence.pddl as a documentation/spec of this transfo

ABS Concept to transform :

• DefinitionGroup
  • AssetType
  • GuardedActions
    • Some Instructions
  • Goals
    • Static Method
    • Some Instructions
• AssetGroup
  • Asset
  • AssetLink

PDDL Concept to Translate :

• Domain
  • Types
  • Predicates
  • Actions
• Problem
  • Objects
  • Init
  • Goal

Improve Transformation (in order) :

• Multiplicity of References
• Unassigner optimization
• Default value
• ForAll/Filter/LambdaExpression
• AssetType Attributes of Enumerated Types and Boolean type
• Code Docs
• Global Optimization
• TESTS, Tests, tests (Larger, more complex examples, ...)
• Multiple Inheritance support

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