Moving into Class-based HTML Components

* HTML_ELEMENT: Now has an ID creation procedure (needs to be fully
tested)
* HTML_TABLE: Added ID creation.
* HTML_TABLE_BODY:  Added ID creation.
* HTML_TABLE_DATA: Added ID creation.
* HTML_TABLE_HEADER: Added ID creation.
* HTML_TABLE_ROW: Added ID creation.
* HTML_TEXT: Added cautions/invariant constraints for no contents and a
`make_with_text'.
* HTML_ELEMENT_TEST_SET: Added tests for duplication of W3-Schools
<table> example in both the long form and short form using a class
instead of creation by hand to show BOTH WAYS of creation.
* TEST_SAVINGS_TABLE: The class-version of a <table> for the W3-Schools
version.