Fix for RPM postinstall on old OpenSUSE distributions

Older OpenSUSE distributions do not ship with systemd and therefore are
using chkconfig, but do not have their scripts placed at /etc/init.d/
This patch is more defensive and adds additional checks in the postinstall
script to prevent aborted post install scripts, which makes the RPM
uninstallable.
Reduce branches in TopChildrenQuery

The branches used in the score method can be moved into the
scorer call and be essentially a constant operation rather than
a linear operation depending on the number of parent docs.
Ensure tests pass if store dir is a soft-link
Renaming span_multi_term query to span_multi

... due to discussing this on #2610 in order to have a more concise name
initial commit
commit 2
commit 3
Added next generation parent-data lookup mechanism for parent child queries.
Cut all the parent-child queries and filter over to the new parentdata infrastructure.
Removed id cache
Moved IdCacheStats stuff to ParentDataStats
Fixed top_children query
commit