VB/IB size warnings

[walbourn]

Add a few warnings:

• If the VB size exceeds the required resource size support by DX11/DX12 D3D11_REQ_RESOURCE_SIZE_IN_MEGABYTES_EXPRESSION_A_TERM * 1024u * 1024u), emit warning.

• If the above error triggers and you are not using compressedvertexdata, note that as an option

• If the overall SDKMESH size exceeds 100 MB, emit warning if you are not using compressedvertexdata (useful for GitHub publishing)