Adds a CheckBlueprintSyntax(...) method to check the syntax of a
Blueprint file.
Changes processModuleDef and newModule from being method on *Context to
being standalone functions. That ensures that CheckBlueprintSyntax(...)
does not need to take a context and so there is no chance that it can
change its state.
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.