Crash reporting

This setting must be configurable in Settings screen.

Default values for the preference:
* _debug_ builds: enabled by default
* _release_ builds: disabled, but can be enabled

Also, would be great to implement manual sending of current log.

Since, we have same feature in Navigator (see https://github.com/ARK-Builders/ARK-Navigator/commit/cf38b61f6306f91fc3b4800fa8bd5e5f822823ef and https://github.com/ARK-Builders/ARK-Navigator/issues/78), it would be great to extract common functionality into tiny lib. We would inject such a lib into all of our apps.

Start by reviewing the referenced ARK-Navigator commit and issue 78, then locate the Settings screen and crash-reporting entry points in Shelf. Clarify the shared-library boundary and verify the debug and release defaults, settings control, and manual log-sending behavior; done means these requirements work in Shelf and the common functionality is reusable across apps.

Written by the indexing model from the issue text.