LP#1635386 Clarify and simplify row highlighting code

LP#1635386 Clarify and simplify row highlighting code

The existing code had a few functional problems for me.  In the process
of fixing them, I decided it best to also apply a number of small
refactorings.  Here is a list of changes in rough order of significance:

-Made the new CSS classes test and apply once per row rather than once
per cell

-Fixed the test case for overdues: we now just look for no checkin-time
+ no lost/long-overdue stop-fines (matches XUL test)

-Made the color and icon tests totally consistent, and also simplified
where possible

-Made the widened configuration header style (to accommodate status
column) functional again (it was using old 'statusicon' class)

-Made row highlight colors '!important' to avoid bad interactions with
alternating row color styles

-Changed status-cell (and statusCell) to status-column (and
statusColumn) for a little extra clarity

-Changed nested function name from 'rowClass()' to 'apply()' for greater
code distinction (i.e. avoid 'rowClass.rowClass()' calls, and instead
have 'rowClass.apply()')

-Removed some unused variable assignments from grid.js

-Cleaned up a few field attributes for necessity and consistency

Signed-off-by: Dan Wells <dbw2@calvin.edu>