Revert "Deprecate no longer used Skin::getCommonStylePath."

Revert "Deprecate no longer used Skin::getCommonStylePath."

This reverts commit 79dcf7686d857e1dcbc3f1127a106d847de10d9e.

getCommonStylePath and getSkinStylePath are a pair of methods for use in 3rd party skins (NOT core).
They cut down on the boilerplate for including skin urls into skins for things like <img> tags.
Without these methods skin authors will be forced to revert to unintuitive boilerplate to add style paths and style versions into their code.
Most won't even bother to include the style version.
And ResourceLoader is a tangent to the whole topic because no matter what the advantages to CSS are developers writing custom skins for a single site from scratch will not care and they will choose CSS or <img> based on situations on hand in their own markup that make one or the other harder to handle.
This addition was part of the effort to fix the longstanding issue that our our skin system does not properly account for 3rd party skin developers.

Change-Id: I98f4fd83c93aba7681306d0a1edb58f798057543