Pyrates

- adjusted the call of the max/min functions: Use `maxi` and `mini` in the equations. Both functions take two input arguments, and return the larger/smaller one, respectively
- updated the PyRates reference in the readme and on the documentation website (using the PLOS CB paper now instead of the arxiv preprint)
- removed a bug where differential equations with a constant right-hand side were not properly handled by the automated compute graph optimization
- resolved an issue with the fortran backend where complex data types were not properly processed during the code generation

- updated readthedocs configuration file
- added keyword argument `adaptive` to the `CircuitTemplate.get_run_func` method, which allows to indicate whether the generated equation file is expected to be called with an adaptive step-size solver (`adaptive=True`) or not
- reduced computational overhead for the creation and simulation of delayed differential equation systems
- removed a bug where edge attribute dictionaries were changed by mistake during the `CircuitIR` instantiation
- improved working directory management in the backend
- dropped official support for python 3.6 and added support for python 3.10

- simplified automated generation of unique variable names. Recursive calls etc. were replaced with look-up tables, thus improving speed during the file generation process.
- improved variable passing between different operators within a node. Less additional variables are now created, thus reducing the memory load during run time.

- fixed bug in fortran backend where the NPAR parameter for Auto-07p files was not properly set
- improved code readability in fortran backend
- moved selection of output variables from the results of a numerical simulation from the backend to the computegraph, thus reducing the amount of variables that had to be passed between the different classes
- after each simulation, the value of all state variables in the compute graph is updated to the value at the final simulation step
- added functionalities to the `CircuitTemplate` that allow to remember the state of all network variables from a previous simulation, even if a new backend is chosen for function generation or more simulations

- added a background input parameter to the izhikevich population template
- updated the documentation example for parameter sweeps to account for recent changes in the keyword arguments to the `grid_search` function
- changed keyword argument `vectorization` of the function `grid_search` to `vectorize`, to be consistent with the naming of the same argument in `CircuitTemplate.run`
- updated the `CircuitTemplate.add_edges_from_matrix` method to allow for edges that connect separate network nodes

This official release is a combination of all the bug fixes and improvements in the
pre 1.0 versions up to v0.17.4.

It establishes PyRates as a code-generation tool for dynamical systems modeling
with a flexible, intuitive, and well organized language for model definition.
At this stage, PyRates comes with support for ordinary and delayed differential equations and can
generate vector-field evaluation functions for any ODE/DDE system for each of the following backends:
- NumPy
- Tensorflow
- PyTorch
- Julia
- Fortran
While PyRates still provides extensive support for numerical simulations and parameter sweeps itself, its main advantage is that it can generate run functions for dynamical systems that can be used in combination with dynamical systems analysis tools in any of the above mentioned tools/languages.