Quality of life improvements for user

[SNMS95]

• Explicit naming of samplers: from grid, random to grid_sampler, randm_sampler etc.
• Explain or eliminate **kwargs in public API e.g. grid documentation says it accepts kwargs but what are the expected arguments?
• Unify ways to execute block. Currently there are multiple ways to do the same thing i.e. with experiment_data.run or with Block.call etc.
• Datagenerator block is confusing since the execute method uses self.experiment_sample without very providing it explicitly.