Simplify Jamf API connection

Currently the Jamf API connection is established via 2 separate calls, such as:
```
JAC = JamfApiConnection(server, username, password)
api = JamfApi(JAC)
```
There was some reason I had to do a 2-step call like this, but I can't remember what it was anymore. Regardless, it's a little silly, and the 2-steps should be abstracted away so it's just a single call such as:
```
api = Jamf(server, username, password)
```

Locate the definitions and usages of JamfApiConnection and JamfApi, then trace how the two-step construction currently passes server, username, and password. Refactor the public entry point to support the requested single-call Jamf form while preserving the existing connection behavior. The work is done when callers no longer need to construct JamfApiConnection separately.

Written by the indexing model from the issue text.