Permission fixes, requirement ordering fix, more. Many changes. Bad dog.

- Simplify deploy-directory references
- Maintain more directory permissions re project owner/group
- Fix multiple-projects requiring same python_version ID clash
- Install virtualenv requirements after libs (reasoning in docs)
- Fix site-pkgs symlink creation
- Fix various requirement ordering
- git_libs pillars restructured to 'libs', with (default) 'git' type
- Miscellaneous refinements :)