Update jquery.multiselect.js

Added isIE offset, IE formats differently than chrome, so there's a new IE only class added.

Modified to work with Jquery UI 10,
Added decision for drop up or drop down, sometimes there's more room upwards.  shrinks height of list if it won't fit in either direction.

Added autoHeight option. . .this will re-size the list to either what will fit in the browser, or to the height of the list, whichever is appropriate.