mgr/dashboard: unify button/URL actions naming

mgr/dashboard: unify button/URL actions naming

- Mappings (actually an Enum) created for actions (buttons and other UI elements) and URLs: ActionLabels and URLVerbs.
  - An alternative would be to fix/improve the current i18n-polyfill, which only works with literal strings (not even with 'const enums' which become literals after Typescript transpiling).
  - Additionally having a predefined file with some strings to translate (actions, verbs, etc) could improve on the 1st of the 2-stage i18n process (as extraction tool has a lot of limitations).
- A corresponding ActionLabelsI18n service with translated labels (it's a service as I haven't found the way to either translate no-const strings (ngx-translate/AST parser failure) or get a static translator).
  - This services could/should be extended to cover all strings that are defined in static/globally scoped objects before any I18n provider has been initialized.
- Breadcrumbs are not translated (neither were they before this change). This part remains untackled: using 'proxy' static objects and performing live translation could deal with the issue.
- New URLBuilder service created (following a established pattern in the Java/.NET world) . This should avoid the need of messing with literal URLs and string composition/parsing, and while the front-end is not meant to be consumed by anyone, Angular does not provide any other way for the app to navigate between components, so the URLs are a de-facto interface contract. Unlike this approach is not flawless, it's easier to enforce, while issues coming from free-from strings are really hard to catch.
  - This could be further improved by using a router registry/dynamic routing. Most of the routes are trivial.
- As a side effect of these changes, routing module has been refactored and some routes moved to their specific modules (pool, rbd, rgw), via loadChildren and routes.forChild() magic. Now the above mentioned components are lazy-loaded/pre-loaded (it means right after the main code is loaded). This should also decrease the loading time (though probably this is not biggest time eater here).
  - As now modules can be loaded multiple times, not only from App module by means of lazy loading, but also from other ones (as PoolModule loads BlockModule to get QoS widgets in Pool windows), now lazy loaded modules include 2 NgModules (one with imports: RouterModule.forChild(routes), meant for lazy-loading, and another without routes).
- Caveat: Some parts might not be (fully) translated (NFS, iSCSI, mirroring), as there's been ongoing work on them and it's hard to keep up with the new code.
These changes will be a waste of time if the new code does not take benefit from/adheres to it, so I'm still figuring out how to spread this (nothing really fancy to demo). Maybe adding some checks/harnessing to enforce the new naming convention (ideas greatly welcome here).

Fixes: http://tracker.ceph.com/issues/37337
Signed-off-by: Ernesto Puerta <epuertat@redhat.com>