fix parsing external network

[mprins]

• Make admin network external in test case
• Make the external attribute of a Network be an Optional boolean

resolves #57

[mprins]

@wst24365888 any chance of #57 being fixed and released with this PR

[kevinjone25]

lgtm, the external attribute should be bool value at lagacy version
compose spec
FYI

[wst24365888]

Hi @mprins ,

First of all, sorry for the late reply, I was in hospital for some time. I've reviewed your PR and it's great, thanks! I found out that our pipeline did not sync the latest compose_spec and convert it to corresponding compose_spec.py, so we'll merge your PR first and fix the sync issue soon.

Again, thanks for your contribution.