Load limited point cloud

[PablerasBCN]

I think it would be nice to have a global variable to load a max point cloud per cloud so if I whant to load 30 tiles each having 9 millions it loads only like 30k points per tile to have an sparse cloud and later on per tile be able to override such value in case I need more detail, instead of hte runtime LOD which is not tha tperformand, also loading big datasets would be way faster