DAR-2396 Temporary logging for SassUtil

The code block gated by
!empty($settings["background-image-width"]) && !empty($settings["background-image-height"])
should never execute.
However, it gets executed, so we need to find out why.

The logging can be turned on and off with a variable.

This will be removed right after defect is fixed.
DAR-2396 Adding missing parameter to Wikia::log
Merge pull request #1785 from Wikia/DAR-2396

DAR-2396 Temporary logging for SassUtil