Optimization to reduce Handle size by 50% [problem] Memory usage is too high, event-thread operations are too heavy. [cause] Too much Dali::Handle data copied around. [solution] Remove all virtual methods from handles, to avoid needing a C++ vptr Change-Id: I87c8c526be53413e895a88ac8a355083a4797d8e Signed-off-by: Adeel Kazmi <adeel.kazmi@samsung.com>