Text formats are now configurables

As a part of #1479454: Convert user roles to configurables the 'filter' and 'filter_format' tables have been removed from the database schema and text formats have been converted to configuration entities (configurables).

Summary

• The 'filter' and 'filter_format' tables have been removed from the database schema.
• Text formats become classed objects a.k.a. \Drupal\filter\Entity\FilterFormat.
• Core and Standard Installation Profile formats are now defined in .yml files.
• Instead of directly accessing format values we now use the appropriate Entity API methods (e.g. $format->label() or $format->id())
• The custom CRUD API for text formats has been removed in favor of a proper Entity API storage controller a.k.a. \Drupal\filter\FilterFormatStorageController.
• The old CRUD methods (filter_format_save(), filter_format_load() etc.) have been removed in favor of the Entity CRUD API. FilterFormat::load() to can be used to a filter format.

API changes

Use the Entity API CRUD functions & methods in the future instead of the filter_format specific functions.
Custom formats previously defined in code through filter_format_save() should be defined through .yml files in the future.
Filter functions that before expect an object now expects a FilterFormat instance.
{filter} and {filter_format} tables are removed, the settings of a filter are now part of FilterFormat::$filter.