Update dependency syntax for "dub init" packages of type "vibe.d".

Keeping track of the saved json file in the journal and some smaller changes.

Make "dub.json" the primary choice for a package description and handle "package.json" as a fallback.

Add a "VibeDefaultMain" version to the package description of "dub init xx vibe.d". ...

This will allow to invert the current VibeCustomMain version at some point to make vibe.d play nicer as a simple library.

Remove dub.internal.std.process compatibility code as it doesn't support browse() and the compile status on older DMD versions isn't tracked anyway.

Extend "dub init" to take an optional type argument and don't create "public"/"views" folders by default. Fixes #152. ...

The generated package.json is also improved WRT the copyright and author strings (using the current date and the local user name).