This restructuring allows for easier separation of modules into
separate repositories later. Also, now pip install with repo url can be
used.

The setup.py files have also been updated to correctly reference each
other. Module versions are not extracted from git state

- was not used consistently before
- symbol names are expected to be valid C identifiers
- for complicated field names, the latex_name of field should be used

- small (length < 5) arrays with shape and stride information had to be
  memcpy'd to the GPU before every kernel call
- instead of passing the information as arrays, the single elements are
  passed
- leads to more function arguments, but simplifies GPU kernel calls

-> changes in all backends required

- not generic enough - does not work if there a multiple blocks

- removed warnings
- added flake8 as CI target

- test run again
- notebooks not yet

- single function to create kernel for specified target
- data type creation from string - reuse numpy functionality
- bugfixes in dot display

Fixed a severe bug. Renamed makePythonFunction of the llvm backend.
Deleted code duplicity.

Added LLVM: CodePrinter and a compiler
Updated data_types
Added tests
Added jupyter notebooks
Fixed bugs
Restructured transformation functions