Developing a server to host a smartphone app content

Im building this app (using Unity3d) for a client and I need to split the content from the actual app since content must be easily changeable without having to update the app itself.

I want to host the content on a server and use http POST messages to retrieve the data. I also need to have a web editor (kinda like a CMS) so that the client can change the app content himself through their web browser.

In the editor I would just have a list of "rooms", where each "room" would be one of three types (i.e. text screen, slideshow or audio). Depending on what type the room is, different parameters should be visible and editable.

What language/tools should I use for this task?

The server will be written in Python but I am not sure how to develop the editor side.