Clear caches in EntityType::save() and Bundle::save() instead of the form submit handlers

Here we go. Most of the changes are pretty non-controversial, I think. The Features Import will suffer a performance decrease after this, because previously the caches were only cleared once after saving all entity types. Now the caches are cleared multiple times. Especially the schema cache clearing and menu rebuilding are heavy I think.

For the latter, though, we shouldn't be calling menu_rebuild() ourselves but doing variable_set('menu_rebuild_needed', TRUE);

Follow-up for that coming.

Here we go. Now the only notable performance decrease is the schema cache clear. Without having benchmarked that, though, I think that's an acceptable drawback to this consolidation of code and (arguably) a bug fix (from the perspective of an API consumer).

I found #1980152: [documentation or bug] drupal_flush_all_caches() does not clear drupal_get_schema() static cache, so we should add the schema cache reset on delete() as well.

Here we go. Bundle did not have a delete() yet, so I added it.

Setting to needs review again.

I'm personally not married to the cache clearing in the API functions, but I do think it is clearer conceptually.
If you're concerned about Performance we could do the cache clearing in shutdown functions. That would probably done in a similar fashion to the 'menu_rebuild_needed' variable. We could simply set a 'entity_cache_rebuild' (or a better name thereof) variable and if that is set, to do all that cache clearing in 'eck_shutdown_function'. Thoughts?