stemcells should be deletable with force

- but only when it isn't being used in a deployment
- e.g. when "someone" nukes the stemcell image from the IaaS
change location and invocation of stemcell-copy script
 - addresses binstub assumption that the script was ruby
 - script moved from deployer gem to bosh_aws_cpi gem as the aws_cpi gem was where it was invoked
allows override of stemcell build path
fix for using s3 blobstore. Retains simple if blobstore plugin is not set
AWS bootstrap: manifest generation matches input files and builds green in system spec
Fix Micro Cloud Foundry build stages.
fix for properties.agent.blobstore
Fix bat:dns tests, added BAT_DNS_HOST env variable
Use sys-filesystem instead of parsing df which might not be portable and it looks better
Relax multi_json dependency version in blobstore_client
Merge pull request #38 from cloudfoundry/micro-json-gem-blobstore

Relax multi_json dependency version in blobstore_client
call included stemcell-copy.sh script with sudo

   we need sudo access to write to aws EBS device for stemcell creation
   luckily we have passwordless sudo access on the default aws ubuntu AMI
add missing update to Gemfile.lock
More BAT fixes plus example BAT_DEPLOYMENT_SPEC
Remove commented out log line
use sudo -p to avoid getting stuck asking for password
Fix sys-filesystem version
Return string for backward compatiblity
Fix test for string values
(nitpicking) Remove rogue whitespace