New: Analysis API Custom Content

You may now perform an analysis on custom content sources uploaded via our Upload API by using the following syntax:

    "FACEBOOK",
    "CUSTOM:pubTypeName"
]```

You may provide multiple custom data sources in a request. But all the sources should be under the same team.

**Changelog**
- added: `CUSTOM:pubTypeName` as valid string in `sources` array
- added: