Allows users to create block instances of predefined block types registered by other modules.
Features
Difference to core blocks:
Modules register block "types".
Administrators can spawn new instances of a block type.
Block instances are entities.
Unless a block type opts out, Block API takes over the storage of configuration settings per block instance.
Major ideas and parts for the block instance handling have been based and borrowed from JohnAlbin's excellent Menu block module.
An example API implementation is available in a hidden testing module, which provides the equivalent of custom blocks in core; i.e., a simple title and HTML body.
Block API itself provides no block types on its own.
This utility Drush add-on just deletes text files (not needed but are) packaged with Drupal; files like INSTALL.txt, UPGRADE.txt, README.txt (in multiple places), etc.