pending fog support; CLI can provision IP address
introducing a wrapper to discover the microbosh fog connection details
bosh_target(_uuid) stored in SystemConfig

SystemConfig#microbosh returns object that extracts
details about the target microbsoh via its
micro_bosh.yml
now need to setup system before testing any defaults/choices
Fix ec2_endpoint regex to extract region for us-east-1
Add missing fog_compute accessor