Puppet: fix apache2 conf missing directory issue

When installing Phabricator on Lubuntu 13.10 it seems that
/etc/apache2/conf.d isn't present, explicitly create it.

Test Plan: provision a fresh Lubuntu 13.10 VM
meta/install_*: split to 2 files, tools + phab

Split the 'install phabricator' concern out of meta/install_devtools.sh
and into a new file of it's own so that the devtools can be installed on
a machine with an alternate or no Phabricator setup.

Test Plan: on fresh VM: $ ./meta/install_phabricator.sh