refactor OppositeLen meta annotations in accordance with server

...b.info/FrameIT/frameworld/$Opposite$Len_$Problem.omdoc.xz

....info/FrameIT/frameworld/$Opposite$Len_$Solution.omdoc.xz

...tp..mathhub.info/FrameIT/frameworld/$Scroll$Meta.omdoc.xz

errors/mmt-omdoc/Library/gearbox.mmt.err

errors/mmt-omdoc/Scrolls/AngleSum.mmt.err

errors/mmt-omdoc/Scrolls/Pythagoras.mmt.err

errors/mmt-omdoc/Scrolls/SupplementaryAngles.mmt.err

narration/Scrolls/OppositeLen.omdoc

narration/Scrolls/ScrollMeta.omdoc

...al/http..mathhub.info/FrameIT/frameworld/$Scroll$Meta.rel

source/Scrolls/OppositeLen.mmt

source/Scrolls/ScrollMeta.mmt