implement new @rend values: marginOuter/InnerLeft/Right

[BOberreither]

Most of the time there's only one correction per line or at least per line and margin. So the @rend values marginLeft and marginRight are enough. In some cases though, there are up to three corrections for one line in one margin. These need to get more precise @rend values, please replace existing values:
marginLeft > marginInnerLeft, marginLeft, marginOuterLeft
marginRight > marginInnerRight, marginRight, marginOuterRight

There are also cases where the correction for a specific line is written a bit above/below line level; please make a list of these cases so we can look at them in a separate run.

There are some cases where this has already been implemented test-wise, just take a look at p. 71 for an example.