[osis-core] 3.2.17. Lines within a line group

[Chris Little]

Dallas issue:
 > Use type="q", type="q2" (or similar type names) and a set of other 
standardized types to indicate the specific nature of the <l> element.

We briefly discussed adding a level attribute to the l element to 
indicate levels of indentation.  ThML does this, I believe.  And 
alternative would be to standardize types like "level1", "level2", & 
"level3".  I do not believe "q" or "q2" should be used--those come from 
SFM and don't communicate much at all to anyone who hasn't used SFM.

This is separate from the <lb> issue.  These would go on l elements of 
genuine poetic lines.

This is in addition to embedded lg elements, which aren't very 
economical to use when lines alternate indentation, as is common.

--Chris