Support name field for parachain nodes

[JoshOrndorff]

Currently launch supports the name field for relay chain nodes in order to quickly insert the -alice flag for example. This also allows the relay chain nodes log files to have nice names like alice.log.

With proper consensus algorithms coming to cumulus in both paritytech/cumulus#371 and paritytech/cumulus#429 parachain nodes will need session keys and will benefit from the name field.

As a side bonus this will allow the parachain nodes to have nicer log file names (eg para200-alice.log) for the alice node on parachain id 200.