Remove knowledge about AppManifest structure

[doosuu]

CLI parses the AppManifest but does not need to care about the actual structure of the manifest. Therefore the structural correct parsing is removed from the responsibility of the CLI with this PR (validity of JSON is still checked).

[github-actions]

File	Coverage	Lines	Branches
All files	76%	86%	67%	❌
src/commands/exec/index.ts	79%	92%	66%	❌
src/commands/init/index.ts	76%	87%	65%	❌
src/commands/package/index.ts	88%	95%	80%	✅
src/modules/component.ts	84%	96%	73%	✅
src/modules/exec.ts	58%	65%	51%	❌
src/modules/package-downloader.ts	85%	96%	75%	✅
src/modules/package.ts	91%	92%	90%	✅
src/modules/project-cache.ts	83%	96%	71%	✅
src/modules/project-config.ts	82%	91%	73%	✅
src/modules/semver.ts	50%	64%	37%	❌
src/modules/setup.ts	24%	33%	15%	❌
src/modules/variables.ts	87%	94%	80%	✅

Minimum allowed coverage is 80%

Generated by 🐒 cobertura-action against 64837cd

[dennismeister93]

lgtm