**Closes #750, #721, #605, #467, #454, #436, #232, #163, #86**

### Many new features and improvements:

1. Expanded on iconSet concept to create linkInfo option to allow configuration of all header link attributes, including icons, text, and titles.s.
2. Menu height can now be dynamically resized via the jQuery UI resizable widget, if loaded and resizableMenu option set to true.
3. Fixed some issues w/ the menu height getting mangled when filtering was in used.
4. Modifed how header option is used.  Can still set to false to hide header, but now it is also used to specify what header links are seen and in what order.
5. The multiselect can now also be used as a fixed list box (always open; no pop-up) via the listbox option.
6. New options groupsSelectable and groupsCollapsable control whether option groups can be selected and/or collapsed, respectively.
7. Option groups can now be set to be collapsable.  A new small button shows up at the left of each option group heading to collapse/expand the option group.
8. New resync and value methods allow quickly updating the widget options checked state from the underlying native select.
9. Can now use the up/down keys on closed single select to change the selected option if the button is focussed.
10. Fixed a previously unknown bug caused by binding menu events to the outer $menu container div instead of the $checkboxes container.  This bug caused the menu events handler to also try to handle header events.
11. Added the ability to reference option groups by their label or index for use as a filter.  Now usable programmatically in addOption, checkAll, uncheckAll, flipAll, collapseAll, and expandAll.
12. Simplified the auto width determination for the _setMenuWidth() method by tweaking the related CSS rules.  As a benefit, the _getScrollBarWidth() function has been eliminated.
13. Updated and simplified the _setMenuHeight() method to allow it to better work with filtering.
14. Re-wrote the filter widget--can now search option group headings and supports alternative filter rules.
15. Updated and added unit tests.
16. Updated demos and changed theme to Redmond--no more ugly construction orange.
17. Updated i18n files for new linkInfo option format.

1. Make optgroup clicks function on the optgroups regardless of collapsed status.  However, filtered status is still observed for excluding from clicks.
2. Fixed issue of filter not working in dialogs.  Apparently, widget instance() method is no longer supported, per StackOverflow thread.  Using .data('ech-multiselect') to fetch the instance now--this works w/ the dialog.
3. When filtering, now hide optgroup headings unless a match on children li's or optgroup heading (if searching optgroup headings option set)
4. Formatting tweaks.
5. Switch to using arrays for list items in options... e.g. header option to specify displayed links in desired order.
6. As IE10+ is IE minimum, switched to using array.indexOf() for array lookups and classList where appropriate.
7. Ditched NOT USED in linkDefaults object.
8. Made _linkHTML() an internal method function.
9. Implemented classes for the optgroup collapse button and the optgroup label anchor.
10. Fixed resync.  find('option') not find('options')
11. Fixed destroy.  '.' prefix on namespace is not optional for .off()  (document listeners issue)
12. Moved single select button up/down code to separate method and simplified that code.
13. Changed bindMenuEvents to bindCheckboxEvents

This reverts commit 1815e57.