ARIA valuenow property only used for numeric values

[becky]

In order to support the Linux a11y API's the valuenow property in Firefox 3 will only support numeric values. Thus, the setValue() api in _FormWidget needs to be updated as well as other uses where a string is being used as the valuenow.

check combobox, progressbar, slider, and spinner as well.

[becky]

(In [11980]) refs #5543 removed use of valuenow in combobox; update of value attribute of editfield is sufficient for a11y

[becky]

updates for form widgets

[becky]

explanation of 5543.patch.

remove setting of valuenow from _FormValidationWidget.setValue() since not all FormValidation? Widgets are numeric. removed _FormValueWidget.forWaiValuenow() - it is no longer needed

added setting of valuenow to _slider.setValue(). Slider needs to set valuenow since setting has been removed from FormBalidationwidget?. added setting of valuemin, valuemax to _Slider.postCreate() - it was an error that these were not being set previously.

removed textBox.forWaiValuenow() as it is no longer needed since textbox is generally not numeric.

added RangeBoundTextbox?.setValue function to set valuenow since it deals with numeric text boxes.

[becky]

progress bar is using valuenow properly

[becky]

(In [11993]) fixes #5543 only set ARIA valuenow for numeric values of spinner, slider and progressbar. More details in ticket comments.