tool_build/package_compiler: added 'modified' property.

tool_build/package_compiler: unset 'modified' property after write().
tool_build/package_compiler: added metadata accessor.
tool_build/package_compiler: added find_resource_id().
tool_build/resource_metadata: new interface.
tool_build/package_compiler: added add_resource() & remove_resource().
tool_build/compiler_manager: added write_packages().
tool_build/interface: write all packages after command success.
tool_build/interface: moved command impls to separate files.