Calkulate

* Renamed many functions and variables, as now described in the conventions documentation;
* Added **plot** module to visualise titration results;
* Updated `halfGran` solver to return values in dict field `'x'` for consistency;
* Fixed fatal bug in `Dickson1981` solver;
* Fixed incorrect `eqConstants['P1']` value in D81 dataset loading function;
* Combined all calibration and VINDTA-style functions into generic functions that can implement any solving method;
* Major documentation overhaul, and added workflow examples.

* Added full outline documentation and function docstrings;
* Added **meta** module, with single-source-of-truth version number;
* Converted lists of solute concentrations (`XT`) and dissociation constants (`KX`) to dicts;
* Renamed *MPH* functions to *complete*;
* Updated various aspects of nomenclature throughout;
* Switched pH simulator to solve for pH, not [H⁺];
* Active efforts towards MATLAB integration paused.

Added `calk_ptl.m` MATLAB function to quickly visualise everything about a titration file.