Sane run_common_test.erl

Backward incompatibility warning:
server configurations are renamed from _configs_ to _presets_; to me _configs_ suggest some connection with `ct:config` or `test.config` while the the server configurations have nothing to do with them; `test_config` make rule is renamed to `test_preset`, the section in `test.config` is now `ejabberd_presets` instead of `ejabberd_configs`. This might clash with some Jenkins script or whatever external tool that relied on this name.

`main` is the only entry point to the script.
`run` is the function which dispatches actions depending on parsed options.
It's now much easier to add options without multiplying the number of entry points.