Values set before applying a template are not removed

[marstamm]

Describe the Bug

When I apply a template, non-templated properties are not removed.

Steps to Reproduce

1. Create a Service Task with "Retries = 3"
2. Apply the Rest Connector
3. Retries is still 3, even though it is not templated and can't be changed anymore

Expected Behavior

All non-templated properties are removed when I apply a template.

Properties like name, multi-instance and interrupting config should still be present, as they have execution semantics

Notes

Follow-up from #32 (comment)

Environment

• Host (Browser/Node version), if applicable: [e.g. MS Edge 18, Chrome 69, Node 10 LTS]
• OS: [e.g. Windows 7]
• Library version: dev