crumbs 7.x-2.0-beta1

Code style, architecture:
- Plenty of docblock comments with type hints added.
- Plenty of changes that make the IDE happy.
- Use injected router object, instead of Drupal functions (might help us with unit tests in the future, dunno)
- Some classes moved around and renamed.
- Use generic crumbs_MultiPlugin_EntityParent for nodes and taxonomy terms, instead of having dedicated classes. Keep the dedicated class for users.
- New interfaces for plugins with findParent() and findTitle().
- New interface crumbs_PluginInterface for both multi and mono plugins.
- Remove unused methods and functions.
- Some dpm() and console.log etc removed.
- Reusable containers for plenty of stuff (might be a bad idea)

Bug fixes:
- Fix the textual weights form that was broken (only available with crumbs_labs)
- some intermediate fixes
- Front link should link to frontpage (empty path), not to 'node'. See #2044949: how to prevent Crumbs from adding /node to the front page link?

API:
- Introduce crumbs_InjectedAPI_hookCrumbsPlugins::routeMonoPlugin() and ::routeMultiPlugin(), for plugins that are restricted to a specific route. This way people can avoid the stupid method suffix to indicate the route.

Features:
- Breadcrumb titles for views with contextual filters
- Weights tabledrag form: Distinct section for "Disabled by default."
- New experimental weights configuration form, only available with crumbs_labs.
- Some tweaking on the tabledrag UI.
- Support i18n_menu.

Tests:
- Crumbs module must be enabled in web test