config-only abstract categories and map/list defs

plugin categories may opt to forego the pluggable annotation
without loss of functionality as long as they include the in-conf,
optional _class specification. Probably mostly useful for 3rd
party classes like those in the standard library.

map and collection interfaces/ abstract classes can use the
_default setting on a plugin map, but for now at least they
cannot make much use of any other plugin map or alias setting. the
default conf file now includes sections for some of the basic
utility types like map, lists, sets, and so on.