Add installation info for jupyter and ZeroMQ

[ssiccha]

Do I have to add a declaration for &ZeroMQ;? If so, how and where?

[fingolfin]

@ssiccha you'd have to define this as an entity -- edit makedoc.g for this

[fingolfin]

BTW, even after @markuspf and @sebasguts told me about pip install --user notebook, I was stuck; a hint to the super beginner about jupyter notebook would be nice.

[markuspf]

@ssicchaha will you add this note?

[ssiccha]

@markuspf Already did, but didn't mention it.

The last paragraph now reads

To start &Jupyter; run:
<Log>
> jupyter notebook
</Log>
Then &JupyterKernel; should show up in your &Jupyter; installation as "GAP 4
(native)". The addition of the "native" qualifier is to distinguish this kernel
from the old kernel that wraps a &GAP; session inside a python script.

[markuspf]

Cheers