Make all ports and network configurable

[gilesknap]

This allows a user to set the range of ports and network subnet that is used by the composed containers.

Benefits

• We no longer tie up the default channel access ports so developer containers can use them instead
• We could potentially run up multiple of these compose projects on a single host
• The changes also incorporate PVA so that the AD PVA plugin is now used in the example project

Downsides

• there is more setup in environment.sh and perhaps it is less legible as a result