comparison operators are not meaningful for times

We should clarify in the spec that the `<`, `>`, `<=`, and `>=` operators are not defined for `LocalTime`.

Why not? Well, because:

1. Time of day doesn't have a meaningful total order. Times form a topological circle. It's not meaningful to say that 23:59:59 > 00:00:00. That's just completely arbitrary. Is the first time a day after or one second before the second time? You need a date to know for sure.
2. Oracle has no ANSI-like `TIME` type, and to emulate it requires jumping through really disgusting hoops.

Start with the persistence specification section covering LocalTime and its comparison operators. Clarify that <, >, <=, and >= are not defined for LocalTime, preserving the rationale in the issue; done means the specification states this unambiguously.

Written by the indexing model from the issue text.