Benchmark example drawing many triangles

[theodoregoetz]

Added vsgtriangles example which can be used for experimenting with large models (many vertices, many draw calls and many pipelines).

We found on several systems a limit on the number of triangles that this program can draw at 1999999 (exactly one less than 2M). Right at 2M triangles, we get a crash with the following stack-trace on linux:

vsgtriangles -n 100 100 200

#0  __memcpy_evex_unaligned_erms () at ../sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S:289
#1  0x00000000004e09df in vsg::TransferTask::_transferImageInfo (this=0x7ffff732b01c, vk_commandBuffer=0x10ddd80, frame=..., offset=@0x7fffffffc0f0: 192000000, imageInfo=...)
    at ~/workspace/vsg/VulkanSceneGraph/src/vsg/app/TransferTask.cpp:258
#2  0x00000000004e0638 in vsg::TransferTask::_transferImageInfos (this=0x7ffff732b01c, dataToCopy=..., vk_commandBuffer=0x10ddd80, frame=..., offset=@0x7fffffffc0f0: 192000000)
    at ~/workspace/vsg/VulkanSceneGraph/src/vsg/app/TransferTask.cpp:212
#3  0x00000000004e1d01 in vsg::TransferTask::_transferData (this=0x7ffff732b01c, dataToCopy=...) at ~/workspace/vsg/VulkanSceneGraph/src/vsg/app/TransferTask.cpp:469
#4  0x00000000004e0e5f in vsg::TransferTask::transferData (this=0x7ffff732b01c, transferMask=vsg::TransferTask::TRANSFER_BEFORE_RECORD_TRAVERSAL) at ~/workspace/vsg/VulkanSceneGraph/src/vsg/app/TransferTask.cpp:320
#5  0x00000000004d9a21 in vsg::RecordAndSubmitTask::submit (this=0x7ffff732ae0c, frameStamp=...) at ~/workspace/vsg/VulkanSceneGraph/src/vsg/app/RecordAndSubmitTask.cpp:93
#6  0x000000000049a9b2 in vsg::Viewer::recordAndSubmit (this=0x7ffff732a4a4) at ~/workspace/vsg/VulkanSceneGraph/src/vsg/app/Viewer.cpp:836
#7  0x0000000000411fc2 in main (argc=1, argv=0x7fffffffcb08) at ~/workspace/vsg/vsgExamples/examples/commands/vsgtriangles/vsgtriangles.cpp:271