primitives

During the work on merging #1419 I figured out that the basic BUFGMUX example works differently on Arty Board and Nexys Video.

The example uses three LEDs:

• led[2] - blinks with slow frequency
• led[1] - blinks with high frequency
• led[0] - blinks with the same frequency as led[2] or led[1] depending on sw[0] state.

On the Arty Board, the example works as intended. On Nexys Video, when

Current save/load methods focus on dumping and loading the pipeline definition in its JSON form, but provide no means to save a fitted pipeline and load it later to make predictions, being the usage of pickle outside of the pipeline the only way to go.

Let's re-implement the save/load methods to save the whole pipeline instance, and move the current save functionality to a to_json method.

For consistency with others, toJSON() should be added to the address types.