Bug 874796 - Add setting to disable / enable cell broadcast alerts.

The setting does not currently effect channel 50 cell broadcast
messages, which will be displayed regardless of this setting.
Bug 880292 - [Contacts] Gmail import is using a personal developer keys
Bug 881193 - Reset mute and speaker status at the first call
bug 881812 - update test-agent
Bug 879563 - Added option for installing external addons. r=ochameau
Merge pull request #10196 from eeejay/additional-extensions

Added option for installing external addons
Merge pull request #10231 from daleharvey/874796

Bug 874796 - Add setting to disable / enable cell broadcast alerts.
Bug 875854 - [Settings] add missing settings to settingsDB. r=vingtetun
Merge pull request #9994 from gregorwagner/settings

Bug 875854 - [Settings] add missing settings to settingsDB
Merge pull request #10312 from crh0716/881193

Bug 881193 - Reset mute and speaker status at the first call
Merge pull request #10326 from lightsofapollo/test-agent-vbump

bug 881812 - update test-agent
Bug 877141 - Strip down non-break spaces from contenteditable

When several consecutives spaces are typed in a contenteditable element,
all but the last one are converted to non-break spaces. We don't want
this, here, so we simply replace them with normal spaces.
Merge pull request #10298 from arcturus/bug-880292

Bug 880292 - [Contacts] Gmail import is using a personal developer keys
Merge pull request #10333 from lissyx/bug877141

Bug 877141 - Strip down non-break spaces from contenteditable

r=julien