Getting error reports with logs of strange behaviour is useful even if
the app doesn't crash.
Move crash reporting in to `core.activity`, and provide a menu option
(in orange builds) to trigger a non-fatal crash report that is handled
the same way (i.e., sent by e-mail) as a regular crash report.
`BaseActivity` has to be able to create and handle menus, so adjust
subclasses to call the superclass when necessary.
Update `tools/mvstring` to be able to move strings between different
flavour directories, not just `main`.
1488c13c42