[Persistence Matrix] Make options, in particular column types, more flexible

[hschreiber]

Not "easy": in my opinion, the original issue is that using an `enum` makes the design not extensible (a user cannot provide their own column type). If you changed the design enough for it to be extensible, then there would be no limitation on parameterizing the column types you provide.
(IIRC, Boost.Graph has a similar limitation with a hard-coded list of possible containers for some data structures)
Without going all the way to an extensible design, using tag classes instead of an enum (i.e. empty classes that are only used with `is_same<T,vector_column_tag>` or similar) might not require huge changes and could accommodate `small_vector_tag<8>`.

Originally posted by @mglisse in #1154 (comment)