Log files per module/ddoc

[ryanramage]

Currently gardener stores/outputs all logs into one stream. it would be nice if each app had its own stream/location. Makes it easier to detangle when things go sour.

I'm seeing per-module log files, with some sort of rotation scheme being used. Is this where you want it now? I was hoping to clean up the file names a bit and maybe provide some flexibility/options for the rotation (e.g. retention length, compression) but I could do that in a new issue post-v1.1.0.