Add 'DELETE' clause support.

The SQL 'DELETE' statement is support but not tested or fully
implemented. A clause object was created and boilerplate added for
creating 'DELETE' clause, but helper functions for the 'Table' object
not implemented or tested.

Additional documentation added to the JSDoc comments.
Add delete/remove helper function to 'Table'

A 'remove' helper function that returns 'Delete' SQL clause was added to
the 'Table' prototype. The 'delete' function name could not be used
because 'delete' is a keyword for JavaScript.
Add test for 'delete' helper function.

Added a test for using the delete helper function of the 'Table'
prototype.

A better way of handling parameters and assembling clauses is still
needed. There appears to be memory effects with parameters in the 'Expr'
prototype.

Signed-off-by: volks73 <cfield2@gmail.com>