Cleanup: move pl.lapp and pl.config into pl.app

[Tieske]

pl.app already has a command line parser, pl.lapp is just a more powerful one. But they are both application level utilities, hence should both live in pl.app.

Since pl.config is also an application level tool, it should also go in pl.app.

[alerque]

Any idea what the history is behind having two app modules and two arg parsers? I don't even think lapp even hit my radar as existing — or I never happened to notice it at the same time as app. Somehow I never realized there were even two implementations.

[Tieske]

I think the lapp one is more commonly used, but I may be skewed towards that one since we use it at Kong...