HG-191 Re-implement Google Analytics event tracking

* Added new GA tracking module
* Changed structure of GA config in localSettings
* Changed UA implementation to older method using ga.js
* Moved tracking JS to head element
* Corrected some typos ;)
HG-191 Use interface for type
HG-191 Code review feedback
HG-191 Additions to GA tracking

* Addressed code review feedback
* Implemented singleton for event trackers
* Added new GA tracking util which wraps page view track
HG-191 Check special wiki for GA
HG-191 Add Mercury property and address comments
Merge pull request #248 from Wikia/HG-191

HG-191 Re-implement Google Analytics event tracking
HG-203 side nav now closes on link-to interactions, side nav also resets now
HG-203 replace double quote in actions with single
HG-203 only use single quotes
Merge pull request #250 from Wikia/HG-203-fix-side-nav

HG-203 side nav now closes on link-to interactions, side nav also resets...
HG-182 implement simple loader
Merge branch 'master' into HG-182-loader
HG-182 use single quotes
fix-empty if article is empty (but it is a valid article page), then show empty message
HG-182 hide loading state on timeout (and other errors)
HG-182 clean up scss
HG-182 remove spinner.scss
HG-182 fix formatting and remove dev code
rename template to match convention