Removed the shell/batch scripts and modified dub to be a stand-alone executable. ...

Also removed all implicit dependencies to vibe.d (such as always specifying the vibe.d source folder using -I).
Fixed expanding of packages with multiple package.json files (the top-level folder inside of the zip archive was detected wrongly).

Compiles using latest vibe.d and DMD 2.061.

Added missing file.

Half working version with some paths fixed (vibe.d must be checked out next to dub).

Initial commit (more or less the same code as used for vibe.d's vpm).