Implement keyword index re-generation

[pheller]

Add a "keyword" property to the Object schema, and a mechanism to then rebuild and insert into the database the objects that comprise the keyword indexes when a keyword is added, removed, or the keyword target is updated.

A new version of TLOT0011.PG ("HIGHLIGHTS"), for example, should not trigger reindexing because the target of the keyword does not change.

When rebuilding these index objects ("TAODCUSS.PGM" and "TAODCUKJ.D*"), the versions of these objects must increment when they change.

To prevent unnecessary objects in the database, should drop all old objects before inserting the new ones (maybe there are fewer keywords, or the secondary index size changes resulting in fewer secondary index objects).

All changes should be done such that client errors are prevented. That is, new objects that add a keyword should be added either before the keyword indices are updated, or all within the same transaction.