Allow tagging a nested property structure with
`blueprint:"filter(key:\"value\")"`, which will only allow property
assignments to properites in the nested structure that are tagged
with `key:"value"`. Moving the filter into Blueprint instead of
the project build logic allows more reliable and consistent error
messages.
Change-Id: I06bc673dde647776fc5552673bdc0cdcd7216462
Make integrating with go tools easier by putting the blueprint package
files in the top level directory of the git project instead of in a
subdirectory called blueprint.
Change-Id: I35c144c5fe7ddf34e478d0c47c50b2f6c92c2a03
