Revise architecture of generators

[OndrejNepozitek]

The current architecture is based on a pipeline that was introduced in an early version of the plugin.

Several things should be considered:

• Do we really need the whole general pipeline? Wouldn't it be better to have exactly exactly 3 steps in the pipeline - input setup, generator, post process?
• Should we keep the payload or should we just manually pass parameters from one step to another? The advantage of having payloads is that there are objects that are needed in all the stages of the generator, for example random numbers generator.
• Should we make it easier to create custom generators based on our architecture?
• Do we still need to keep the pipeline dynamic by pairing configs and tasks?