Memory Pool Logging

Memory Pool Logging

Added methods to fetch the current capacity of graphics memory pools
Added an environment variable DALI_MEMORY_POOL_INTERVAL to trigger
logging of Core memory pools on a timer, and Graphics memory pools
from inside the render thread.

Added logging to PixelBuffer to log individual allocations (By setting
DALI_LOG_PIXEL_BUFFER_SIZE to "1" or higher, and enabling debug).
Added method to PixelData to log total allocation (By setting
DALI_OBJECT_PROFILER_INTERVAL to a non-zero value and enabling debug).

Change-Id: Ib65e16d33d7219456d0245bfe686c199dcfa330f