Allow addition of multiple RDE rows in one action

WIP allow basic fill of a RDE column

WIP basic js refactor to introduce contexts for setting up each fill form

WIP introduce basic sequence form (not working yet)

Add ability to apply a sequence to a RDE column

WIP remove reliance of column indexes from RDE javascript

WIP add ability to reorder columns

Re-enable sticky columns, remove unrequired js/css, and allow toggle between the fill and reorder panels

I18n all new RDE strings

Fix sequence fill.. still refering to indexes

Rebuild the section header row when the columns are reordered
Add new RDE selenium tests.. plus fix add-row not working in firefox