Added script for fetching tile metadata

[rkoster]

Script to create copy pasteable code for updating tile resource data:

./util/pivnet_meta.sh elastic-runtime
elastic-runtime/2.3.3
Small Footprint PAS:
config.PivnetMetadata{
"elastic-runtime",
220833,
254473,
"1ab242bff8f95598193b0c742b7d6a520628ebeb682fd949d18da5ef6c8e5c7a",
},
Pivotal Application Service:
config.PivnetMetadata{
"elastic-runtime",
220833,
254457,
"5540900a3626b092bffdb01b530791a116cf5f1022fd1b048edaeea4424318fd",
},
Ubuntu Xenial Stemcell for Google Cloud Platform 97.31:
config.PivnetMetadata{
"stemcells-ubuntu-xenial",
225315,
259369,
"6b1c333f382770a5f351362f2c8142b7fd165fe9dd96a902bd4e40006f87a650",
},
"light-bosh-stemcell-97.31-google-kvm-ubuntu-xenial-go_agent",