Makes reset_data work with secondary indexes.
Remove an RSI.
Adds post construction function for sindexes.

This is a function to construct the sindex for data that was already
present in the table at the time of creation. This function is, as of
this commit completely untested (and unused). Tests come next.
Adds the start of a unittest for post construction.

Right now it does everything but actually post construct the sindex. That comes
next.
Adds a unittest for post construction which is broken.

This makes it clear that we need to right a better access control method
for the btree.
Makes the post construction test work.

I'm scared I broke something but all unit tests pass...
Finishes off the unittest for post construction.

Things seem to be working.
Sindexes now post construct on creaton.

Except that it's broken because of the fact that our access control
pattern for BTrees is just crumbling around me.
Makes post construction work for query language created sindexes.

Next up is making it work for backfills.
Adds sindex post construction.

In theory as of this commit sindexes are feature complete.
Removes some RSIs

Some of them weren't mine.