Ux branch bugs cherry picked

[\#804166](https://bugzilla.mozilla.org/show_bug.cgi?id=804166) - [Settings] Device Storage Memory Usage Bar Needs Redesign
[\#815653](https://bugzilla.mozilla.org/show_bug.cgi?id=815653) - [Settings] - remove :active for explanation items
[\#816067](https://bugzilla.mozilla.org/show_bug.cgi?id=816067) - [FTU. UX VD] Change background.
[\#816135](https://bugzilla.mozilla.org/show_bug.cgi?id=816135) - [Icons - Assets] Need assets for all the wifi icon scenarios.
[\#823414](https://bugzilla.mozilla.org/show_bug.cgi?id=823414) - B2G browser gradient value does not match the gradient found in Settings
[\#823472](https://bugzilla.mozilla.org/show_bug.cgi?id=823472) - [FTU UX VD] Replace "Hello" bubbles illustration asset in lenguage selection
[\#828908](https://bugzilla.mozilla.org/show_bug.cgi?id=828908) - [Settings] Hints should not be treated as list items
[\#830111](https://bugzilla.mozilla.org/show_bug.cgi?id=830111) - [Settings] - arrange Phone lock screen
[\#830127](https://bugzilla.mozilla.org/show_bug.cgi?id=830127) - [BB][input_areas] - pointer-events is not correct
[\#834102](https://bugzilla.mozilla.org/show_bug.cgi?id=834102) - [Browser] Too much padding to left of address in address bar
[\#834446](https://bugzilla.mozilla.org/show_bug.cgi?id=834446) - [Browser] Truncated Bookmark Label