Added options to control "save packages" behavior:
1. you may now replace "UmodelSaved" directory with something custom
2. added option "keep directory structure" (enabled by default) - now saved packages will be stored with full folder structure of original game content.
Hint: if you want to extract all pak files of some UE4 game, you may use command line:
umodel -save -path=... *.uasset
You can't change "save packages" options from the command line, however you may edit umodel.cfg file if you want to change them without using UI (or if you're on linux).