Remove floor, ceiling for integer symbols

See merge request !14

fix compiler options for macOS

See merge request !12

Stephan Seitz authored 5 years ago and Martin Bauer committed 5 years ago

- rename header Field.h is not a unique name in waLBerla context
- add PyStencilsField.h
- bindings were lacking data type

functions like absolute values could not be used in CUDA backend since
known_functions was replaced instead of updated

Add CudaBackend, CudaSympyPrinter to extract CUDA-specific code from CBackend, CustomSympyPrinter
Cuda built-ins are added to CudaSympyPrinter.known_functions to use them as sympy.Function

# Conflicts:
#   pystencils/cpu/cpujit.py

- version has to be obtained from file when no git repo is available
  like in tar-ball distributed by pypi

- backend, target and compile are now normal members of the
  KernelFunction node and populated in constructor

Destructuring field binding

See merge request !4