remove unused report variable from test utility
change how status and preg_month / child_age are calculated

the main change is updating the window logic to be valid according to
the period that ends N months from the anchor date as per
https://docs.google.com/a/dimagi.com/document/d/1Wu3vZWTbVTYw_oFH10SwgOuY37e7iMyCuHDbyX2zM_E/edit

also includes a fairly sizeable refactor including:
- pull status, preg_month and child_age into properties
- make it clear in the row it is only one month/year
- make datespan calculated from the month/year
- get rid of window entirely
- make end be the first of the next period and update filters to not be inclusive

also updates a subset of tests
fix birth spacing tests based on new window calcs
fix vhnd tests based on the new window calcs
fix preg and child conditions based on new birthspacing calcs
only return vhnd info if the mother meets the right status
fix datatype issues
fix condition 4 calcs based on the updated spec, and update tests
add new method for determining vhnd attendance + tests
tweaks to make report work in the UI again, bring back window
fix age displays on report
fix check for whether there was a VHND and update tests

previously this wasn't properly accounting for the absence of a VHND
as the visit not happening. this also converts the vhnd mapping to
sets of dates for a future logic change to windows based on the date
of the vhnd
add vhnd dependency to mother window calcs + tests
pull out vhnd adjustment
add vhnd adjustment to child month calculation

also changes the behavior so that childs before their first birthday
are not valid instead of returning month 0

adds tests for both conditions
change the child vhnd property to not use the calc and update tests
use the correct child dict property (child_1, not child1) in calcs
properly handle vhnd_date availability in preg and child age determination

refactors the data provider slightly
add logic to look back in the first window for vhnd calcs if necessary
formatting