Issue 835 speech warnings

[TShapinsky]

Settings have been implemented. Now the features need to be implemented:

• Solar Activity Warning
• Wind Speed
• 400ft ceiling exceeded
• low signal strength
• lost signal
• Autopilot-reported errors

[m4gr3d]

@TShapinsky nice catch!

[squilter]

Thanks @ne0fhyk . I think I got it right this time.

[m4gr3d]

@squilter great! It looks pretty good.. Only thing remaining, the two methods above should use context.getString(...) to retrieve the preference key, just like getSpokenStatusInterval() above them.

[squilter]

@ne0fhyk But getSpokenStatusInterval() uses prefs.getString(), not context.getString(). Which one should I use?

edit: nevermind, I might need glasses.

[m4gr3d]

@squilter if you're using android studio, you might not be seeing context.getString(...) as AS collapse the call into the string it's supposed to return.

context.getString(...) is used to provide the first parameter to prefs.getString(..., ...).

[squilter]

@ne0fhyk How's #944 coming? If it's not ready, I can just hide the checkboxes for wind speed and solar activity so that this pull request is ready. Then I'll implement those later.

@arthurbenemann Take a look at my low battery warning here:
TShapinsky@e033876#diff-d41d8cd98f00b204e9800998ecf8427e
Is there a better way to do this? Because I know that the Battery% is BS. The beeper connected to the pixhawk seems to beep when the battery is low, regardless of whether the battery started out full. So clearly the flight code can recognize a low battery properly. But does it send this via mavlink anywhere? (edit: fixed)

[squilter]

I hid the checkboxes for solar activity warnings and wind speed warnings. Those will be implemented after #944 . For now, this PR is ready.

[m4gr3d]

@squilter I should be able to complete #944 later today. The functionality provided by @alextel69 is good to go. There were a few bugs he missed though that I'm fixing.