attribute values for page (and column etc.) ranges are suppressed in the output

[peterstadler]

During Council f2f our subgroup was tasked with PR #348. While we wholeheartedly agree with the desire to change this, we identified several corner cases that should be addressed here as well:

• other units, e.g. 'column', 'line' (see att.citing)
• no @to supplied but only @from
• @from and @to and text content