Support for Different Families of Models

What's Changed

• Refactored code to support adding different model families (e.g phasor dynamics, power electronics).
• Added PowerElectronics family of models.
• Prototype for sparse system matrix assembly (for PowerElectronics only).
• Added PhasorDynamics family of models.
• Unit testing framework.
• GridKit now depends on Sundials >= 7.0.

Release v0.1 by @pelesh in #83

Full Changelog: v0.0.7...v0.1.0

Power flow input file parser and system composer

• Added parser for Matpower files.
• Added system composer, which assembles power flow models from components based on input from Matpower file.
• Updated bus and created generator factory.
• GridKit now depends on Sundials >= 6.0.
• GridKit now requires C++17 compliant compiler.
• Bug fixes.