app/config: Add a value for location of pid file for sphinx

The init script provided with sphinxsearch debian package requires
correct location of pid file of sphinx, so that it can run on system
start-up. So this value is now initialized with a variable `sphinx_pid_file`
in database.php.template so that it can be used to set the location
of pid file in sphinx's init script as well
Fix typos
Merge pull request #412 from Tatoeba/configs-mod

app/config: Add a value for location of pid file for sphinx