- libs() singleton method for global library handling
- explicit handling of empty filename for dlLibraryTable open/close.
Largely worked before, but now be more explicit about its behaviour.
- add (key, dict) constructor and open() methods.
More similarity to dimensionedType, Enum etc, and there is no
ambiguity with the templated open().
- construct or open from initializer_list of names
- optional verbosity when opening with auxiliary table,
avoid duplicate messages or spurious messages for these.
- basename and fullname methods (migrated from dynamicCode).
- centralise low-level load/unload hooks
- adjust close to also dlclose() aliased library names.
