- check that fixed size kernels are called with arrays of the correct size
- checks that layout of compilation matches runtime layout
- not allowed any more to mix fixed & and variable sized fields in a kernel

- version with weights in the entropy denominator

and not as a string.
Changed name of the file TypedSymbol to types.
Fixed usage of dtype accordingly, however i might not have found every
usage of dtype.

- support for different #ghost layers at each coordinate limit

- added sphinx files for documentation generation
- collected kernel creation functions in new "cpu" and "cudagpu" modules