Add the skeleton and first bits of implementation for a semi-dynamic container widget
This introduces the beginning an partial implementation of the DynamicRowContainer. Unlike the regular RowContainer class this will support a dynamic (hence the name) number of elements and pagination.
However, unlike the RowContainer (or ColumnContainer) it will only allow the child elements to have a specific size and ratio. The size is calculated based on the desired number of rows and the number of elements per row as well as an aspect ratio.