Add support for FMMosaicCellSizeTall and FMMosaicCellSizeWide.

Requesting two new sizes FMMosaicCellSizeTall and FMMosaicCellSizeWide.

The way I am imagining it is that FMMosaicCellSizeTall would be the height of two FMMosaicCellSizeSmall (and the width of one) and Wide would be the width of two (and the height of one). 
