refnx/refnx v0.1.3

0.1.3 GUI machinery can now use Components other than Slab, such as LipidLeaflet (already added). New Components may require extra shim code to be written for them. Specifically how they're to be displayed, and a default way of initialising the Component (which may require a dialogue). The 'Link equivalent parameters' action has been added, enabling equivalent parameters on other datasets to be linked. This greatly aids setup of multiple contrast datasets. All the datasets to be linked must have the same type of structure. The initialisation of a LipidLeaflet is made much easier by using a library of lipid head/volumes and scattering lengths for popular lipids which are presented to the user in an initialisation dialogue. The refnx paper is accepted and the article and manuscript file are included in the repository. The pyqt GUI to refnx can be made into standalone executables for Windows, macOS. Fixed a bug that meant most reflectivity calculations were single-threaded instead of multi-threaded. Added MixedReflectModel to the pyqt GUI, allowing one to model 'patchy' systems, i.e. incoherent averaging of reflectivities. BACKWARDS INCOMPATIBLE CHANGE: the slabs properties of Component and Structure have now been changed to methods, taking the optional structure kwd parameter. The reason for this is so each Component knows what kind of Structure it is in. The Spline Component can be used within the pyqt GUI. In the pyqt gui Components can be re-ordered within their host structure by drag/drop. Dragging to other Structures copies the Component to that structure. Added the Stack Component. A Stack contains a series of Components, and the Stack.repeats attribute can be used to produce a multilayer repeat structure. Folded in a reduction pyqt gui for Platypus data. The app was already in the slim directory. It's now available from refnx.reduce.gu