Merging sections

When deep-copying sections, non-section elements applicable for merging replace each other:

# default
## grouping
configuration:
setting 1 = parameters
setting 2 = parameters

# specific << default
## grouping
configuration:
- setting 1
- setting 2

... would resolve specific to this ...

# specific
## grouping
configuration:
- setting 1
- setting 2

Here is another example of this, replacing the configuration fieldset with an empty field instead:

# default
## grouping
configuration:
setting 1 = parameters
setting 2 = parameters

# specific << default
## grouping
configuration:

... would resolve specific to this ...

# specific
## grouping
configuration: