Support complex numbers

See merge request pycodegen/pystencils!72

Bugfix: textures should be implemented as textures without changes

See merge request pycodegen/pystencils!73

Add __str__ representation for TextureDeclaration

See merge request !74

Add option to omit globals when printing C code

See merge request !75

Run opencl without pycuda

Closes #15

See merge request !77

correctly print RNG nodes

See merge request !78

- bugfix: loop counter of vectorized loop now correctly stored as SIMD vector with entries i, i+1, i+2, ...
- basis for in-kernel boundary handling

Fix printing of sp.Infinity/sp.NegativeInfinity

See merge request !71

For sympy, oo s a number. So pystencils prints a type infinity a double
INFINITY as INFINITY.0

Fix error in README.md: pystencils[pyopencl] -> pystencils[opencl]

See merge request !70

Small fixes

See merge request pycodegen/pystencils!69

Declare LoopCounterSymbols nonnegative

See merge request pycodegen/pystencils!68

This removed some checks like `ctr1 <= 0` from my kernels

Set assumptions for TypedSymbol/cast_func/IntegerFunctionTwoArgsMixIn the SymPy way

See merge request pycodegen/pystencils!66

Bugfix: this bracket should not be here (collate_types returns single type)

See merge request pycodegen/pystencils!63

Bugfix: Align calculation of number of ghost layers on GPU with CPU version

See merge request !65