+C API:
+ - Introduce sg_activity_set_t and deprecate wait_all/wait_any/test_any for
+ Exec, Io and Comm.
+
+Plugins:
+ - Revamp the battery plugin: rewrite completely the API, for a better usability.
+ The examples were updated accordingly.
+ - Revamp of the Photovoltaic plugin: now called SolarPanel and complete rewrite of the API
+ - Add chiller plugin: enable the management of chillers consuming electrical energy
+ to compensate heat generated by hosts.
+
+Kernel:
+ - optimize an internal data structure (replace boost::circular_buffer_space_optimized by
+ std::deque to store pending and unmatched Comms in Mailboxes). It is actually a revert
+ to what was used a few years back. The boost structure had a lower memory footprint than
+ deques, but it appeared that their "space_optimized" character was generating a huge lot
+ of refcount changes on the stored Comms.
+