Documentation about API authorization and POST parameters is out-dated

**Describe the bug**
The readme states that the a combination of [ApiKey]:[ApiSecret] is used for authorization at the endpoint. This is not correct as the file "Server/Auth/ApiAuthorizationFilter.cs" expects an authorization string that uses a Base64 encoded version of [ApiKey]:[ApiSecret]

Also some parameters of POST requests changed from a capital first letter to a lowercase first letter.

**To Reproduce**
Steps to reproduce the behavior:
Perform a GET request on "/api/Devices" with authorization header and receive an 403 status.
Perform a POST request as described in the readme, which will fail.

**Remotely Version**
Serve: latest

**Expected Behavior**
Readme communicates the correct way to authorize and also the POST parameters are correct

Review the README instructions for authorization and POST requests, then compare them with Server/Auth/ApiAuthorizationFilter.cs and the documented /api/Devices request. Update the README to describe the Base64-encoded authorization value and the current lowercase POST parameters; verify the examples match the expected GET and POST behavior.

Written by the indexing model from the issue text.