misc: move JamiTheme and JamiStrings to net.jami.Constants namespace

src/mainview/components/WelcomePageQrDialog.qml

src/qmlregister.cpp

src/settingsview/SettingsView.qml

src/settingsview/components/AccountProfile.qml

src/settingsview/components/AdvancedCallSettings.qml

src/settingsview/components/AdvancedConnectivitySettings.qml

src/settingsview/components/AdvancedJamiSecuritySettings.qml

src/settingsview/components/AdvancedMediaSettings.qml

src/settingsview/components/AdvancedNameServerSettings.qml

src/settingsview/components/AdvancedOpenDHTSettings.qml

...settingsview/components/AdvancedPublicAddressSettings.qml

src/settingsview/components/AdvancedSDPSettings.qml

src/settingsview/components/AdvancedSIPSecuritySettings.qml

src/settingsview/components/AdvancedSettings.qml

src/settingsview/components/AdvancedVoiceMailSettings.qml

src/settingsview/components/AudioSettings.qml

src/settingsview/components/AvSettingPage.qml

src/settingsview/components/BannedContacts.qml

src/settingsview/components/BannedItemDelegate.qml

src/settingsview/components/ChatviewSettings.qml