ksgen: use logger specific to module

Change-Id: Ib362ccd77e80b27be1fb7846dea472d8786786dd
ksgen/loader: settings_tree -> settings

Change-Id: I88c92db7254f6ece7c0adca28178be6e080f495f
ksgen/generate: refactor generate into a class

Change-Id: I157df701013a4eb90f26245bf3c64c6029326e64
ksgen/core: move generator to settings.py

Change-Id: Icca520018b45feac6ad7ef884cb8096da77a2c94