Change platform reference for tiles

[gmaniak]

Summary of changes

• Check tile build targets against all known devices not just the ones present in the global build targets list
• Include tile for platforms that have an associated watch component
• Allow tiles just for native bundles

• Add unit tests for new functionality

  Summary of testing

  Bundles are generated correctly.

• All tiles present in bundle have an associated watch component
• Tiles that don't have an associated watch component are not included in the final bundle
• A warning is issued if we try to build tiles without native components

Signed-off-by: Catalin Ghenea gcatalin@google.com

[coveralls]

Coverage increased (+0.1%) to 73.873% when pulling f27efa77f1dbb530108b6c1bfa4f23dabefa5f49 on gcatalin/change_platform_reference_for_tiles into b99687a8b27031f128889340442e6cf0c33004ed on master.