Myokit

- New model syntax, model stars with: `[[model]]`.
- Various small bugfixes.

- Added binary version of `save_state` and `load_state`.
- Added ProgressPrinter to show progress during long simulations.
- Added precision switch to `prepare_log` and `load_csv`.
- Added method to find solvable equations dependent on one or more variables.
- Improved support for ABF protocol and data reading.
- Various small bugfixes.

- Improved OpenCL simulation error output.
- Various improvements and bugfixes.

- Improvements to GUI.
- Improved `find_nan` method in OpenCL sim.
- Added method to expression's `eval()` to evaluate with numpy.Float32 objects.
This helps finding the source of OpenCL single-precision NaN errors.
- Various small bugfixes.

- Refactored code, reduced size of giant modules.
- Various small bugfixes.

- Added recovery-from-inactivation experiment.
- Updated `ActivationExperiment`, added boltzmann fit.
- Added boltzmann fit to `InactivationExperiment`.
- Added time constant of activation method to `ActivationExperiment`.
- Rewrote unit system.
- Various improvements and bugfixes.