Add more details about file api error into exception

[dimitrystd]

If error happen in FileApi, then client doesn't have enough info about error. An example not clear was it a general error or just maintenance

 StringResponse stringResponse = this.inputStreamToString(response.getEntity().getContent(), charset);
            if(response.getStatusLine().getStatusCode() != 200) {
                throw new ApiException(stringResponse.getContents());
            }

DoD: ApiException must contains more details:

• Status code
• Error code (General_Error; Maintenance; etc)
• Error message