Previously, when a document had a leveloffset attribute this was
included in the attributes used when loading a snippet in the
operation block macro. This could lead to warnings about section
titles being out of sequence as the level used for the title did not
take the leveloffset into consideration.
This commit clones the documents attributes and removes any
leveloffset attribute before loading a snippet. This removes the
need for the leveloffset to be considered when loading a snippet
fragment. As before, the level of each block in the fragment loaded
from snippet is then set prior to adding the block to the main
document. This takes the leveloffset into consideration.
Closes gh-649
bb7aecbfe5