port LHCb MT developments to Gaudi master

among others we have

• Gaudi::Functional: base classes to write algorithms as pure functions
• AnyDataWrapper/AnyDataHandle: helper to store any type in the Transient Store (DataSvc)
• fixes to DataObjectHandle
• fixes to GaudiHive
• new tests and examples
• modernization (range loops, removed empty destructors, ...)

GaudiAlg/GaudiAlg/Consumer.h

+#ifndef GAUDI_FUNCTIONAL_CONSUMER_H
+#define GAUDI_FUNCTIONAL_CONSUMER_H
+
+#include <utility>
+#include "GaudiAlg/FunctionalDetails.h"
+#include "GaudiAlg/FunctionalUtilities.h"
+
+namespace Gaudi { namespace Functional {
+
+   template <typename Signature, typename Traits_ = Traits::useDefaults> class Consumer;
+
+   template <typename... In, typename Traits_>
+   class Consumer<void(const In&...),Traits_>
+   : public details::DataHandleMixin<void,std::tuple<In...>,Traits_> {
+   public:
+       using details::DataHandleMixin<void,std::tuple<In...>,Traits_>::DataHandleMixin;
+
+       // derived classes are NOT allowed to implement execute ...
+       StatusCode execute() override final
+       { return invoke(std::index_sequence_for<In...>{}); }
+
+       // ... instead, they must implement the following operator
+       virtual void operator()(const In&...) const = 0;
+
+   private:
+       template <std::size_t... I>
+       StatusCode invoke(std::index_sequence<I...>) const {
+           try {
+               (*this)( details::as_const(*std::get<I>(this->m_inputs).get())... );
+           } catch ( GaudiException& e ) {
+               ( e.code() ? this->warning() : this->error() )
+                   << e.message() << endmsg;
+               return e.code();
+           }
+           return StatusCode::SUCCESS;
+       }
+   };
+}}
+
+#endif