Nayuos: ebuild management improvement, changes to bashrc
- Automatically increment ebuilds revision number.
- Add Chromium browser policies (to use an ebuild which set Duckduckgo as default search engine).
- Improve git configuration in bashrc (export environment variable instead of creating an alias).
- Export EDITOR environment variable in bashrc (so that git does not complain about not finding nano).
- Keep portage_stable overlay clean (stash changes after building).
@tc's commits reviewed by me