Update source code download structure. de-emphasize /docs/assets and docs HTML now that they're outside of the root dir

BS3 commits: 096a72d8975e41f395cea4e3e84aec1744d25165,
56b5f5b353254402b8e999d9ff003d00b7e381ac
flip order so sentence reads better

BS3 commits: 007d61cfadc6f962fc3abc7119f7b9d68f7cd204