add where clause to work order items

I was confused why `items()` was returning different values than LIMS's
website.  Then I discovered that they have a status.  I think it makes
sense to add the where clause.  Originally, I was also going to add an
all_items without the clause but I don't know if we really ever care
about non-active work order items.
simplify xitems

I don't know why this function exists but it's equivalent to `items()`.
remove commented code/footers
remove documentation
limiting to active excluded completed
Merge pull request #126 from nnutter/work_order

two simple changes to work orders