More speech output

[squilter]

Make speech output configurable. Create a preference window for speech. List could look like this (check boxes indicate items already implemented):

Fully implemented with settings-----------------------------------------------------------------------------

Periodic:

• Battery Voltage
• Altitude
• RSSI
• Airspeed

Almost fully implemented in #1012 -------------------------------------------------------------------------

Warnings:

• Read errors when arming fails (prearm check notifications #696)
• 400 ft exceeded
• Solar Activity/wind speed (Enviroment/weather notifications #846)
• Low Battery
• Low RSSI
• Lost signal

Not yet implemented---------------------------------------------------------------------------------------

Missions:

• "Going to Waypoint X"
• Sent parameters/ loaded parameters
• "Mission Complete"

Events:

• Arming/Disarming
• Mode changes
• "Following"
• altitude changes
• gps accurracy changes
• battery 10% increments

Also important:

• Localization of speech output settings

[arthurbenemann]

Lots of functionality was added by #997.