add REST documentation for mediacore module

Yes, Swagger UI just provides a `textarea` for input of JSON objects. However, there is a (not completely intuitive) way to make it somewhat easier. Best show via example:

Click on the "Model Schema" text on the right side.

![screen shot 2014-07-14 at 1 03 28 pm](https://cloud.githubusercontent.com/assets/1731910/3574095/e081f506-0b79-11e4-9f66-bed28d33721b.png)

Then, as the instructions indicate, click on the model schema that is shown in yellow.

![screen shot 2014-07-14 at 1 03 39 pm](https://cloud.githubusercontent.com/assets/1731910/3574104/02b7b17e-0b7a-11e4-8e8a-53b36599cf80.png)

That will pre-fill the `textarea` with a stubbed object.

![screen shot 2014-07-14 at 1 03 49 pm](https://cloud.githubusercontent.com/assets/1731910/3574119/1c427778-0b7a-11e4-9188-1e2778264792.png)

BTW, the [Swagger specification](https://github.com/wordnik/swagger-spec/blob/master/versions/1.2.md) does indeed say:

> If paramType is "body", the name is used only for Swagger-UI and Swagger-Codegen. In this case, the name MUST be "body".

I had previously considered (actually, more than considered, I tried it out with a few endpoints) documenting these parameters as FORM parameters rather than BODY parameters. It sort of works, but seems really hacky and might cause problems in the future.