add servicedir entry at live addon. Add enabled at configuration group entry. Move status entry from path to live addon

This commit sign the end of the "[WIP] allow to switch between trees" works.
The tree directory was used with s6-rc. Tree are now completely handled by
resolve file. That's means that services are not independent of a tree.
Again earn of flexibility.

revamp 66-init. Provide option to only init enabled service or disabled service or all service of a trees

Stop a crash in 66-init when it is used without any arguments.  argc is never 0 so the "if (!argc) " statement won't print the usage.