* Update bpdocs to filter nested properties by tag
Prior to this change nested properties tagged with `blueprint:"mutated"`
are erroneously included in documentation, this corrects that behavior
and adds testing to verify.
Tested: go test bpdocs tests
Change-Id: I822c9a98276634d2f584d8709e83003824cdffd5
Blueprint is a meta-build system that reads in Blueprints files that describe
modules that need to be built, and produces a
Ninja manifest describing the commands that
need to be run and their dependencies. Where most build systems use built-in
rules or a domain-specific language to describe the logic for converting module
descriptions to build rules, Blueprint delegates this to per-project build
logic written in Go. For large, heterogenous projects this allows the inherent
complexity of the build logic to be maintained in a high-level language, while
still allowing simple changes to individual modules by modifying easy to
understand Blueprints files.