Add Date and DateTime CFs to bulk update

Date conversion is needed only for delete because AddValueForObject
in RT::CustomField calls CanonicalizeValue methods to handle
conversion on add.

For Date and DateTime, pass undef for Default to assure that we
don't incorrectly imply that there will be a default value set
if the box is left empty. This inconsistency has been resolved in
4.4 via 4.4/date-input-keep-value

@values is checked for length, otherwise empty string values
are submitted for empty fields resulting in update messages
noting "Not set changed to Not set".
The subroutine ref is called handle, not handler.

This has been wrong since the docs added in 7252c037.
The code was merged into core in b426cccd.  The commit doesn't say where
it merged from, so I can't go further.
Merge branch '4.0/add-date-datetime-to-bulk-update' into 4.0-trunk
New doc for writing RT extensions
Merge branch '4.0/writing-rt-extensions-doc' into 4.0-trunk
allow to toggle off cf's textarea and input sizes if $Cols/$Rows are set to undef

we have default $Cols/$Rows in /Element/EditCustomFields, so it doesn't help
much in core for now, but this gives customers the flexibility to toggle off
the size/cols/rows html attributes for some custom fields, e.g.

    <& /Elements/EditCustomField, ..., Cols => undef &>
Make it possible to use Simplesearch with a different placeholder text

While RT uses Search, RTIR wants to use Search incidents
Merge branch '4.0/simplesearch-placeholder-text' into 4.0-trunk
uninitialized warning fix when cf's Category is undef
div doesn't have "name" attribute, use "data-name" instead
Merge branch '4.0/div-name' into 4.0-trunk
Merge branch '4.0/toggle-off-cf-input-size' into 4.0-trunk
add type="text" to Freeform CF

Browsers FF and Chrome render <input> differently if 'type="text"' is
present or not. Also, this makes the HTML more explicit about the
rendering type.
Merge branch '4.0/incorrect-handler-in-makeclicky-docs' into 4.0-trunk