UI for slicing and dicing.

The user can

- map hierarchies to axes, e.g. display measures on columns and crossjoin(products, customers) on rows
- select individual members for the slicer, e.g. set a filter on year 1998
- select multiple members for display on an axis, e.g. instead of all customers show only customer A and C.

## Classdiagram

The packages member and hierarchy are independent of each other.