Review new scrolling table styles and add to FSS demo

scrolling table was added to fss-layout with these styles:

/* scrollable table with fixed header */
.fl-table-scrollable-container

{ /* space for fixed header */ position:relative; padding-top:2em; }

.fl-table-scrollable-area

{ max-height:160px; overflow: auto; overflow-x: hidden; overflow-y: auto; }

.fl-table-scrollable-area table thead tr

{ /* fixed table header */ left: -1px; top: 0; position: absolute; }

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Make sure the naming convention is correct, will work generally (right now just used in uploader), then add an example to the FSS demo.