dissolve mediawiki::config::*

* Get rid of mediawiki::config::base entirely
* Move mediawiki::config::php to mediawiki::php, express concrete and granular
  dependencies.
* ensure => absent igbinary.ini since we no longer use the extension.
* Work around Puppet 2.7 parser bug by temporarily renaming
  role::mediawiki::jobrunner to role::mediawiki::job_runner.

role::mediawiki::* is still in awful shape, but I'll sort that out in
subsequent patches.

Change-Id: I64401129b28461a268725a002d266f0a2c2967bb