Creation of new property/field for elements

formindex.php is the DB patch for existing sites
mysql.sql is the DB definition for new installs
elements.php is the element class that needs to be aware of the new
field
Creation of admin UI for new option

element.php gathers saved values and sets them up for the template.

element_names.html creates admin form element that is used to set this
new option on and off. Note use of naming convention that will trigger
automatic saving, no specific save handling required. Note also use of
jQuery to set the checked status of the radio button, based on value
coming from element.php.

admin.php sets the language constants used in the template.
Respect new option at runtime

When there is no value saved for an element, and this option is turned
on, then we don't use the blank value as the default for the element, we
treat the element as if it's being shown to the user for the first time
(ie: retain its existing default value if any)

Also, renamed $i to $element for readability.
Bug fix in previous commit

We need to gather $value from $prevEntry before we can determine if it
is empty or not.

if(!$value) at the top of that block refers to whether a value came back
for this element, from the form submission that led to this page, or
not.

Also amended the logic so required fields are treated this way also.  A
required field, by definition, should not be empty in the database, so
if something has happened to make it empty, we'll ignore that blank
value and use the default instead.
Moving new option to Advanced tab

Since required fields are now treated the same way, it makes sense for
this additional option to be declared "Advanced" since it would be used
in fewer circumstances.
Merge pull request #96 from jegelstaff/Use-Defaults-When-Blank

Use defaults when blank