UI for adding new anchors. Sort anchor class coverage tables

This PR adds some features:
1. Add UI when trying to add a new anchor class, not requiring a lookup for the anchor class
2. FF complains if coveragetables from anchor attachment classes are not sorted. FF should sort these. This patch adds that sorting and makes FF happy again.
3. Allows openFile() to specify that all TTF tables be loaded, even if unknown (openflags=32)
Yes. Not sure how to cherry pick that out. But that code isn't used anywhere, so it's debatable as to its value.