Improve docblocks in crumbs_InjectedAPI_hookCrumbsPlugins and crumbs_CallbackRestoration.
Use the short-hand crumbs()->KEY instead of crumbs('KEY'), to allow IDE type hints.
crumbs_InjectedAPI_hookCrumbsPlugins::getCallbacks() becomes ::getModuleCallbacks().
distinguish callbacks by callbackType to allow for different types of callback. For now this is only 'routeParent', but others will follow.
Smarter exception message if crumbs_InjectedAPI_hookCrumbsPlugins forbidden methods are called from implementations of hook_crumbs_plugins().
Introduce \$api->routeTitleCallback() in hook_crumbs_plugins().
Introduce \$api->entityParentCallback() and \$api->entityTitleCallback() in hook_crumbs_plugins().