add setting to enable/disable Link Previews

...c/main/java/cx/ring/account/JamiAccountSummaryFragment.kt

...d/app/src/main/java/cx/ring/account/RegisterNameDialog.kt

...app/src/main/java/cx/ring/adapters/ConversationAdapter.kt

.../app/src/main/java/cx/ring/application/JamiApplication.kt

...rc/main/java/cx/ring/fragments/AdvancedAccountFragment.kt

...p/src/main/java/cx/ring/fragments/ConversationFragment.kt

...android/app/src/main/java/cx/ring/service/BootReceiver.kt

...android/app/src/main/java/cx/ring/service/DRingService.kt

...ain/java/cx/ring/services/SharedPreferencesServiceImpl.kt

...id/app/src/main/java/cx/ring/settings/SettingsFragment.kt

...in/java/cx/ring/tv/conversation/TvConversationFragment.kt

...android/app/src/main/res/drawable/baseline_preview_24.xml

ring-android/app/src/main/res/layout/frag_settings.xml

ring-android/app/src/main/res/values/strings_preferences.xml

...ebase/java/cx/ring/application/JamiApplicationFirebase.kt

...rc/main/kotlin/net/jami/account/AccountWizardPresenter.kt

...in/kotlin/net/jami/account/JamiAccountSummaryPresenter.kt

...ain/kotlin/net/jami/conversation/ConversationPresenter.kt

...src/main/kotlin/net/jami/conversation/ConversationView.kt

...d/libjamiclient/src/main/kotlin/net/jami/model/Account.kt