Audit/fix dir confusion
Ref: Github ticket 69 https://github.com/i2p/i2p.i2p/issues/69
When we set up split install in 0.7.6 (2009) I included not two but four dir settings: install, config, router, and app. The last two default to config and that's what everybody uses. Except Gentoo who sets all 4 different. Comments in I2PAppContext line 225 document the intent.
We aren't consistent in the code about strict separation among the last three and it's untested.
In particular WorkingDir migrates everything to config dir and ignores router and app dir settings. That plus possible wrong choices elsewhere (grep getRouterDir and getAppDir) make a mess for any 4x split setup.
TODO