ScaledTime NumberGenerator now always casts time values to float
Moved transferfn.py to the __init__.py of the new transferfn module
Introduced the Scale transfer function for constant scaling
Added initialize method and init_keys parameter to transfer functions

Some transfer functions may require the shape of the numpy data before
execution for correct memory allocation (eg. TransferFnsWithState) or
may need the coordinate system of the array. The initialize method
provides a mechanism to makes such information accessible to the
transfer functions as necessary.
PatternGenerators initialize output functions in set_matrix_dimensions
Fixed implementation of equality operator for BoundingBoxes
Convolve added as first concrete component of transferfn/sheetTF.py