Update and improve RVM dependencies

**Prerequisite:** This pull request assumes that #229 will be merged first (dependency on `maven` cookbook, not on `maven3` cookbook)

**Solved Problems:**
- `gawk` is now required by RVM (on Debian-based platforms)
  (see https://github.com/wayneeseguin/rvm/commit/45a85047d7f45b42cfcd8dd15eb95c1cfed1fe62 and
  https://github.com/wayneeseguin/rvm/commit/4baf7d90d35d278ab891781d3237e18cebd47b5a).
- `maven` is now required (instead of `ant`) to build JRuby head
- Explictly depends on `sqlite` cookbook

I also propose to removed outdated metadata.json (this file is not required by chef solo, and should be generated from metadata.rb)