* added container template parameter to allow choosing between e.g. list and vector
* changed container type from Events::Set<T> to Events::SetPair<T> because event sets are always picked by successive start/end pairs

base renderer doesn't deal with chronologies anymore, this has to be done by child classes
it now provides minimal functionality (i.e. only combine3 method for now) and has a pure virtual method getNextSetPair which must also be implemented in child classes
the orphaned endings systems has been removed because Chronology should not allow orphaned endings

* renamed nearly all impl classes/files + added new ones
* updated include paths and class names wherever needed
* AbstractPerformer is the base Performer class inheriting from Renderer::Provider
* AbstractPerformer has a protected Renderer but doesn't implement Provider pure virtual methods
* top level classes are children of AbstractPerformer : they implement Provider methods and have a Chronology

* added armed / playing / stopped internal state
* added callback setter to allow listening to emitted note events
* anti voice stealing is now a utility (not a strategy anymore)
* added a history of anti voice stealing states to restore it anytime the index jumps
* new peekNextSetPair method returning the next set pair to be rendered by render (useful for playback)
* setCurrentIndex emits all pending note off events, resets all state, then sets the state to armed

…again. Crash comes from somewhere in render (combine3?)

…setChronology that caused a segfault when calling render (e.g. from the ossia binding)

* MINOR : set current index to 0 after setting chronology. Now crashes again. Crash comes from somewhere in render (combine3?)
* Fixed non-initialization of local performer state in case of call to setChronology that caused a segfault when calling render (e.g. from the ossia binding)

We need to update the avs from avsHistory in two cases :
* we just looped, which means currentIndex == minIndex
* we moved the cursor manually and called setCurrentIndex, which means we are in Armed state

The "memory" and "functional" headers were used (for std::shared_ptr and 
std::function respectively) but not included. This could break the build 
in some environments. It has been fixed.

As per issue #24