Age checks

[gbook]

Ages can be incorrect based on varying information entered for the DOB and age-at-study. Display the following checks and assign NULL values where appropriate to identify unknown information.

• Store unknown DOB as NULL. Allow user to enter NULL for unknown birthdates. Assume empty string is null.
• Store unknown age-at-study as NULL
• Display NULL DOB, age-at-study as 'unknown'

study_ageatscan appears in the following files

• analysisbuilder.php
• batchupload.php
• groups.php
• import.php
• projectchecklist.php
• projects.php
• search.php
• studies.php
• subjects.php
• timeline.php

birthdate appears in the following files

• analysisbuilder.php
• audit.php
• beh.php
• cleanup.php
• groups.php
• import.php
• index.php
• merge.php
• projectchecklist.php
• projects.php
• reports.php
• search.php
• stats.php
• studies.php
• subjects.php
• timeline.php

[gbook]

added StudyAge function to functions.php added checks to groups.php