Better audio recording quality. [Issue #2204]

This is an attempt to fix
https://code.google.com/p/ankidroid/issues/detail?id=2204

The solution tries to enable higher sampling (16 kHz) encoding where possible, otherwise it falls back on MediaRecorder's default instantiation (=current behaviour).

While I am aware that a successful usage of MediaRecorder.OutputFormat.AMR_WB expects devices having minSdkVersion=10, I kept regardless minSdkVersion=8 in the manifest with the fallback implementation in mind.
I reckon this will still allow it to work on devices with Android Sdk 8 and 9. I admit I am not an Android expert.

Tested successfully with a Samsung Galaxy S4 Mini (Sdk=17), with build target Sdk=19. 
Yes, there is. [`MediaRecorder.OutputFormat.AMR_WB`](http://developer.android.com/reference/android/media/MediaRecorder.OutputFormat.html#AMR_WB) has been introduced in API 10 (Gingerbread_MR1).