Rewrite dumper in Go (#49)

Rewrite dumper in Go

Differences:
- All APIs are fully qualified in both the options (`--must-exist=certificates.cert-manager.io`, `--ignore=deployment.apps`) and the output files (`objects-Certificate.cert-manager.io.json`).
  This makes it possible to distinguish between objects with the same kind but different groups. See #47.
- Resources without a list endpoint are ignored, do not cause an error, and don't need to be explicitly ignored.
- Ignore and must-exist options are now command line flags instead of files in `/usr/local/share`.

Fixes #47 and maybe #42.

Merge pull request #20 from projectsyn/fix_bugs

Fix bugs

Merge pull request #20 from projectsyn/fix_bugs

Fix bugs

Merge pull request #18 from projectsyn/various_fixes

Various fixes

Release v0.2.0

Merge pull request #11 from projectsyn/prepare-release-0.1.1

Prepare release v0.1.1

Merge pull request #7 from projectsyn/release

Release v0.1.0