Myokit

- Updated licensing info.

- Myokit can now be installed as library using `python setup.py develop`.
- Fixed a bug in the gnome scripts that install icons.
- The `DataLog` `trim`, `itrim` and `extend` methods now return copies, instead of modifying the data 'in place'.
This makes the `DataLog`'s methods more consistent, and prevents accidental data loss.
However, this change makes Myokit 1.26.0 slightly backwards incompatible.
- Added a `DataLog.keys_like` method to iterate over 1d or 2d logs.

- Small tweaks to IDE
- Fix to `DataLog.fold()` to discard remainder if period doesn't exactly divide the log length.
- Various bugfixes.
- Improved cvode error catching.
- More control over `lib.fit` verbosity
- Added random starting point option to lib.fit methods.
- Added the option to explicitly specify log points in the single-cell `Simulation` class.
- CVODE sim now raises `SimulationError` if maximum number of repeated zero-steps is made, instead of plain `Exception`.
- Fix `fit.cmaes` to work with cma version 2.x

- Small tweaks to IDE.
- Fixed bug with saving the time variable in `DataLog.save_csv()`.

- Added xNES and SNES optimisation methods.
- Added interface to CMA-ES optimisation method.
- Replaced the 'tolerance' arguments `in myokit.lib.fit` with more accurate counterparts.
- Removed `ga()` optimisation method.

- Added model export to Stan.
- Added data-clamp to CVODE simulation (works, but generally a bad idea).
- Added Protocol.add_step convenience method for building sequential step protocols.
- Added `log()` method to `ExportError`.
- Fixed bug in ABF reading (ABF channel index can be greater than number of channels in file).
- Small fixes to `DataLogViewer`.
- Fixed issue with PySide file open/save dialogs.
- Several small fixes to docs.