EHN: manageSubProject.php optimization

Use a php array object to cache all subproject objects, make sure
we only query db once for every subproject.
EHN: Optimize subprojects stats query in index.php

Modify the query to use group by to retrieve a specific stats
for all subprojects instead of query each stats for every individual
subproject.
Merge branch 'cdash-r3547-tango-dev' of github.com:jcfr/CDash into overview_v2
Merge branch 'overview_v2' of github.com:jcfr/CDash into overview_v2