Introduce new module rdiff-backup
Change rdiff default options
Remove backup::params
Refactor backup::agent to define
Simplify backup agent/server
Unify shebangs
Inline bash variables
Revert "Inline bash variables"

This reverts commit 347face03e9645f77fcca3f8c1735257c23bfbfa.
Merge pull request #319 from njam/issue-319

Move rdiff-backup to separate module