1) fixed DateUtils to use SimpleDateFormat for everything because it respects Locale
2) added getCurrentLocale() method to DynamicLanguage
3) allow PassphraseRequiredActionBarActivity.initFragment() to accept a Locale
4) updated classes that depend on DateUtils to pass down Locale from DynamicLanguage
Fixes#2684Closes#2725
// FREEBIE
1) Migrate from GSON to Jackson everywhere.
2) Add support for storing identity key conflicts on message rows.
3) Add limited support for surfacing identity key conflicts in UI.