add BrooklynClassLoadingContext and pass it around when we are instantiating,
fixing BrooklynComponentTemplateResolver.loadEntitySpec to use new loaders from CatalogItem.

currently BCLC does not really pull his weight, as he is just used for instantiation and is never combined or kept;
but as we fix deeper bugs in trying to resolve classes from the purview of another,
i think it will become very useful.

(already it should be the case -- but needs testing -- that BCLC allows children to be resolved WRT
the parent's bundle if they are not declared as catalog items)