Instead of using the more rollup-tolerant config for all files, make the
configuration stricter by default but lower in grunt for yui modules.
This means that manual runs (prechecker) or editor integrations will
flag up the errors as well as grunt.
Also add ignore lines to the core files so that eslint isn't noisy when
not running with grunt.
Most of the moodle core dialogue types should be shown modally, and
centred. They should also be shown on instantiation.
Rather than re-define all of these settings, this patch introduces a new
subclass of M.core.dialogue which sets them up with the same settings.
