Extension of Mesh for Polygons

- added SubentityMatrixType to MeshSubentityTraits and modified SubentityMatrixType in MeshTraits to get SubentityMatrixType from MeshSubentityTraits based on Dimension and Subdimension template arguments
- refactored template argument EntityTopologyDimensionTag of SubentityStorageLayer back to EntityTopology to allow specializing for Polygon
- added Polygon specialization for MeshSubentityTraits that uses different SubentityMatrixType and leaves out any count related defined types
- added Polygon specialization for SubentityStorageLayer, that unlike SubentityStorageLayer used in other cell topologies, additionaly stores subentiesCounts
- added setSubentitiesCounts function to mesh and its storage related parent classes for setting subentitiesCounts in SubentityStorageLayer
- modified getSubentitiesCount function in mesh to pass the unused entityIndex parameter to StorageBaseType::getSubentitiesCount to enable retrieving variable subentitiesCounts from Polygon specialization of SubentityStorageLayer