- 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

- moved simplification strategies from lbmpy to pystencils
- better notebook display for simplification reports
- additional demo and documentation

- version with weights in the entropy denominator

Although expressions have args and function as a tree, args cannot be
modified. So tree-transformations are not possible.
Sympy has subs function, however it replaces all matched in any
subexpression, of the expression (i.e. not only in args but in args args
and so on).

Move my llvm demo notebook in the correct folder

- colored dot output of AST
- various display helpers used in documentation

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.