Harmonize SG names and types

[dinkelbachjan]

Naming of SG models has become quite heterogenous. We envision the following nomenclature:
SynchronGenerator<OrderNumber><OptionallyModelVariant><SolutionMethod>
Example: SynchronGenerator6aVBR

Abbreviations for possible solution methods:

• Delayed Current Injection Method (DCIM)
• Predictor Corrector Method (PCM)
• Voltage Behind Reactance (VBR)

Also GeneratorType has become quite heterogenous. We could envision the following:
enum class GeneratorType {PVNode, IdealVoltageSource, IdealCurrentSource, [DifferentialEquationSystemModels]}

Where [DifferentialEquationSystemModels] enumerates the models describing the synchronous generator in terms of a differential equation system. The entries could look as follows:
Order<OrderNumber><OptionallyModelVariant><SolutionMethod>
Example: Order6aVBR