setTextValue() refactor

[bill]

Rename setTextValue() to setDisplayedValue(), and move it from Textbox to SerializableTextBox? (since it only makes sense when the hidden value and a displayed value are different).

Also, rename SerializableTextbox? to MappedTextbox?. SerializableTextbox? is a bad name since even a simple Textbox can be serialized (trivially) by just copying the value of the textbox.

[Douglas Hays]

setTextValue in Textbox.js should probably be made private, leaving _DropDownTextbox to implement the parent setTextVaue for DateTextbox?, AutoCompleter?, and Select. I don't think SerializableTextbox? (aka MappedTextbox?) needs a setTextValue since it doesn't have a way to unserialize a text value.

[Douglas Hays]

(In [8729]) Fixes #1176, #1740, #3032, #3086, #3095, #3101, #3129. Proxy commit for haysmark. Code reviewed by bill and doughays. Support for page up/down in AutoCompleterMenu?. setTextValue refactored to setDisplayedValue. Added key handler for DropDownTextBox? so DateTextbox? has basic key support. InlineEditBox? now sets isEmpty to false when the input is indeed nonempty. DropDownTextBox? no longer hides MasterTooltip? if it is already hidden. Updated test_InlineEditBox DateTextbox? and Select widgets to use the correct attributes. Cleaned up test_AutoCompleter and test_Select attributes. Consolidated onkeypress page up/down with arrow up/down. Fixed several code-style issues.