Myokit

- Added unit methods to IDE.
- Updated the installation guide.
- Added method to 'walk' over the operands in an expression, depth-first.
- Added a few default unit representations
- Various small bugfixes.

- Added unit checking methods.
- Improved CellML unit reading from constants.
- Added `pack_snapshot()` method that creates a copy of the current Myokit version.
- Created `DataBlock` classes for alternative view of rectangular simulation data.
- Added GUI for viewing 1D and 2D simulation data.
- Various small bugfixes.

- Changed `[[plot]]` to `[[script]]`.
- Various improvements and bugfixes.

- Updated interface of opencl simulations.
- Added OpenCL-based parameter RangeTester class.
- Various small bugfixes.

- Updates to documentation.

- Improved documentation.
- Added a 'running simulations' guide.
- Added SymPy export.
- Added unit tests.
- Added binary format for simulation logs.
- Aliases are now retained in model export.
- Various small bugfixes.