Adding "dump:index" and "dump:manifest" commands

```
usage: zinc dump:manifest [-h] -c CATALOG -b BUNDLE -v VERSION [-O]
                          [--no-decompress]

optional arguments:
  -h, --help            show this help message and exit
  -c CATALOG, --catalog CATALOG
                        Catalog reference.
  -b BUNDLE, --bundle BUNDLE
                        Bundle name.
  -v VERSION, --version VERSION
                        Version.
  -O, --remote-name     Write to file using remote name instead of stdout
  --no-decompress       Don't decompress file
```

```
usage: zinc dump:index [-h] -c CATALOG [-O] [--no-decompress]

optional arguments:
  -h, --help            show this help message and exit
  -c CATALOG, --catalog CATALOG
                        Catalog reference.
  -O, --remote-name     Write to file using remote name instead of stdout.
  --no-decompress       Don't decompress file after downloading.
```

Example:
```
$ zinc dump:manifest -c games -b pancakes -v latest
```
Would dump the manifest json to stdout