Overhaul to several pieces of functionality.

* improved the resize detection to be a little faster (i.e. not
  dependent upon the css) and thus more reactive and less mis-click-y;

* restrict the drag of the column to be within the header area
  (i.e. at same Y coord);

* added an option for specifying the number of non-resizable columns
  distinct from the number of non-reorderable columns;

* added a callback for resizing so that we can resize the FixedColumns
  plugin scroll wrapper;

* added the ability to resize a column from the left hand side (I kept
  misclicking and it was annoying).

* Also now style the reorder highlighter and the drilldown column
  header cursor.
Do our best to make sure that table columns match up with the headers
(i.e. within minimum size constraints); fixed table resize to index
the proper <th> tags within the corresponding <thead> of the scroller.
Merge commit 'efc771e' into ColReorderWithResize