Add Sites for resources and data sources

[ecanault]

Hi,

This is a followup of #12 to request Sites support for resources and data sources.

Description

Classic API Endpoint for Sites is described here:

• POST request to create a new site https://developer.jamf.com/jamf-pro/reference/createsitebyid
• PUT request to update an exising site https://developer.jamf.com/jamf-pro/reference/updatesitebyid
• GET request to obtain site details https://developer.jamf.com/jamf-pro/reference/findsitesbyid
• DELETE request to remove a site https://developer.jamf.com/jamf-pro/reference/deletesitebyid

Endpoint URL: https://yourServer.jamfcloud.com/JSSResource/sites/id/{id}

Sample request body for PUT and POST:

<site>
    <name>Minneapolis</name>
</site>

Required parameter for every type of request:
id, set to 0 for a POST request.

Sample Go code for each method is available on the pages above, but I don't have the knowledge to develop this by myself.
I hope I'm doing it the good way to ask this, and thank you for creating a PR if you find this enhancement helpful!