Changes:
* MinervaUI will now prefix any icons with `minerva`
* Update definitions in skin.json, retaining selectors for cached
HTML for icons that are rendered via PHP.
* In I9021c53c2c04bdd7ce395eed33d89986acbfea6d watch and watched
and arrow are moved to MobileFrontend so are removed from the RL module
skins.minerva.icons.images.scripts as they are not
used directly in this repo. user and anonymous are no longer used
so also removed.
* Presentation of userpage now belongs to MobileFrontend. Icons
are styles were moved there in depends on. They are retained in
skin.json to support cached HTML as user pages are subject to
cache. They can be removed in a week.
* In code review we noticed the anonymous icon was badly named. We
rename to login. No caching implications.
* Main menu icons are now prefixed with minerva rather than mf to
reflect where they come from.
Depends-On: I9021c53c2c04bdd7ce395eed33d89986acbfea6d
Bug: T182162
Change-Id: I93264024f4915fc910c792b1905b89cdc6b8b546
c5d09c0288