Fixed upgrading/install logging of ~master dependencies.

Renamed everything "vpm" to "dub".

Implemented basic build platform detection and extended the possibilities for platform specific fields in package.json.

Added the possibility to specify "dflags-xyz" in addition to "dflags" for platform specific flags. ...

Can be one of:
 - dflags
 - dflags-platform
 - dflags-architecture
 - dflags-platform-architecture

where platform is "windows", "linux", "posix" etc. and architecture "x86", "x86_64", "mips" etc. (the lowercase version of the predefined D versions)

Note that the platform is currently hard-coded to windows-x86

All dub specific files are now stored in a .dub subfolder.

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).