Feature Compare attr order defined by config

Rather than allowing the order from the mxd to determine the display
order
user the ordering of the fields specs in the compare config
Set plugin window below app modals

Both save 'n share and export had a lower z-index, resulting in the
plugin window being above the modal overlay.  Plugin window is sitll
above all the other map UI elements.
Merge pull request #250 from mmcfarland/fix/fc-field-order

Feature Compare field order