Merge branch 'RefactorPrint'

- Modifies printing model to be similar to glabels-3.x.
   - Allow simple projects to print by-the-page (#51)
   - Added collated vs uncollated document merges
- Added ability to separate merge groups by page
- Updated man pages
- Updated misc developer documentation

glabels/icons/flat/32x32/glabels-merge-group-page.svg

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