Teach ExecutionPlans to remember the Ast.
Merge branch 'aql2' of ssh://github.com/triAGENS/ArangoDB into aql2
Sort out variable usage in variable bound expressions.

Not yet compiling, need to sort out access to the Ast object.
Merge branch 'aql2' of ssh://github.com/triAGENS/ArangoDB into aql2
Fix a but where a type argument was unused.
Ignore unused parameters.
Ignore an unused parameter.
Remove an unnecessary parameter.
Restructure who has Ast and ExecutionPlan.

Not compiling yet.
Finish removal of type argument in create.
Finish reorganisation of Ast and ExecutionPlan usage.
Merge branch 'aql2' of ssh://github.com/triAGENS/ArangoDB into aql2