Gerbil Release Roadmap: the road to v1.0

[vyzo]

We are in the future now (see #776 #777) and we can finally explicitly say it: we are on the path for Gerbil v1.0.

Here is the current release plan:

• Gerbil v0.18; Nimzowitch
  This is what we have been frantically working on the last few months, and it is coming close.
  This release is the foundation for everything that follows; many major subsystems are now in their final form, and so is some very important tooling.
  We have also finally achieved full self-hosting; there is no need for an external Gambit dependency (it is integrated as a submodule) and gsi outside bootstrap.

• Gerbil v0.19; Benko
  This is where the language becomes feature complete.

• Gerbil v1.0; Najdorff
  This is where the language is ready.