[Bug 912508] Implement "X has left the call" banner.

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First approach, style needed
Change approach, working with event
Style fixes
Cleaning
Moved banner to call screen
Added tests
Bug 915684: Fix for url var not in scope after refactor. r=alive
Merge pull request #12113 from fcampo/Dialer-ConfCall-bug912508

[Bug 912508] Implement "X has left the call" banner (r=etienne)
Bug 914599 - Improve Call Settings when FDN is enabled

When the Fixed Dialing Numbers options is enabled, many features are
disabled, and USSD/MMI codes fall into this set. This will thus make the
many call settings parameters getting into error state. The present
commit aims at: avoiding undefined state of the call settings, and
improving the feedback we send to user by clearly stating that call
forwaring options are unavaiable due to FDN enabled.
Merge pull request #12172 from comoyo/oop_fix

Bug 915684: Fix for url var not in scope after refactor. r=alive
Merge pull request #12158 from lissyx/bug914599

Bug 914599 - Improve Call Settings when FDN is enabled, r=kaze
Bug 892523 - [User Story] Email Invocation from Notification
Bug 915722 - Remove invalid json for wallpaper mcc/mnc customization. r=arcturus
Merge pull request #12174 from jrburke/bug892523-email-from-notification

Bug 892523 - [User Story] Email Invocation from Notification r=asuth
Merge pull request #12175 from acperez/bug-915722

Bug 915722 - Remove invalid json for wallpaper mcc/mnc customization. r=arcturus
Bug 914886 - [Settings] Use aria-disabled instead of disabled class
Merge pull request #12096 from eeejay/bug-914886

Bug 914886 - [Settings] Use aria-disabled instead of disabled class. r=kaze