refactored RenderJobTemplatesPersister to not modify instance

Signed-off-by: Nick Wade <nwade@pivotallabs.com>
extract database interaction from RenderedJobTemplatePersister

Signed-off-by: Nick Wade <nwade@pivotallabs.com>
merge Hasher and Persister into RenderedJobInstance

JobRenderer#render now returns a RenderedJobInstance

Signed-off-by: Nick Wade <nwade@pivotallabs.com>
inject logger into JobTemplateLoader

Signed-off-by: Nick Wade <nwade@pivotallabs.com>
extracted job template rendering into bosh-director-core gem

Signed-off-by: Mike Stallard <mstallard@pivotallabs.com>
ensure go agent stemcell has a apply_spec.yml available outside image

Signed-off-by: Mike Stallard <mstallard@pivotallabs.com>