Add support for DragonFlyBSD ...

- Switch from /bin/sh to /usr/bin/env bash
- Ignore temporary and test-build files (gitignore)
- Untrack changes to source/dub/version_.d
- Handling 'isDragonflybsd'
- Use 'tr -d' instead of 'tr --deleted' which works on Linux and BSD based platforms
- Fix FRONTEND = unbound variable (test/run-unittest.sh)

USe a default package name for single file packages in case none is ...

provided