Separate creating dummy file from creating file with content.
Check for initialization through given_filesystem
Factor out function to create JSON from manifest
Fix tests
Gnerate release manifest from generic one for KF5
Use "describe" instead of "context".

Use "describe" to express grouping of tests instead of "context",
which expresses a specific environment for tests.
Give explicit access to generic manifest
Implement creation of release manifests for KF5.