Refactor block-override-functions as extendable classes

[bobbingwide]

For issues #27, #30, and #31, and the original issue #7, I've developed a solution that's not particularly extendable.
I want to deliver my solution as a fix for the issue(s) I've raised on Gutenberg.

But, I don't know how to deliver the solution to Gutenberg such that it can then go into core.

Proposed solution

• Attempt to refactor the solution using classes
• Implement classes that extend the base class to produce block specific problem determination support.

[bobbingwide]

In the first refactoring there was only one class Fizzie_Block_Recursion_Control
This contained both the recursion control and the error reporting.

In the second refactoring there will be three classes:

Class	Description
Fizzie_Block_Recursion_Control	Keeps track of nested blocks
Fizzie_Block_Recursion_Error	Reports the recursion error to the front end
Fizzie_Block_Recursion_Error_Blocks	extends Fizzie_Block_Recursion_Error for reusable blocks

The three public APIs will be:

• fizzie_process_this_content( $id, $block_name );
• fizzie_clear_processed_content();
• fizzie_report_recursion_error( $message, $class );

plus

• fizzie_maybe_override_block filter function

There are parameter changes which will have to be applied.
The implementing files will be in the includes folder

File	Contains
class-block-recursion-control.php	Fizzie_Block_Recursion_Control
class-block-recursion-error.php	Fizzie_Block_Recursion_Error
class-block-recursion-error-block	Fizzie_Block_Recursion_Error_Block
block-override-functions.php	4 public APIs
block-overrides.php	control routine for Fizzie's block overrides

[bobbingwide]

Delivered in v0.1.0