Added  support for multiple select

- select.pet.php and input.pet.php are now capable of selecting multiple
values in select tags
- a problem has been discovered in Database_Utility, introduced in the
migration to prepared statements
$parameters has been renamed to $_parameters

this change solves an ambiguity problem introduced in the migration to
prepared statements.
Fixed select "multiple" single item inf recursion

When a select marked as multiple has a single item, it creates a where
clause that used to trigger an infinite recursion. This has been fixed,
this type of where clause is now properly supported.
Performance improvements

Added some convenience methods to avoid calling isset when not needed.
This means less calls to the database and an overall improvement on
performance of the ORM.
Added ErrorMessage method to Database

Also: fixed statement execution, a defect introduced in the migration to
prepared statements.
Fixed typo in NeglectStart
Fixed success verification for database execution