add PIString::lineNumber() method

add ""_tr literal to translate string by PITranslator
add pip_tr util, now useless, only can generate *.ts
add qt_support internal lib, now only works with *.ts file
pip_vtt migrate to qt_support

libs/main/application/pitranslator.cpp

@@ -66,6 +66,11 @@ void PITranslator::loadConfig(const PIString & content) {
 		for (const auto & s: cn.children())
 			c->add(s.name(), s.value().toString());
 	}
+	auto c = s->createContextInternal("");
+	for (const auto & s: lang.children()) {
+		if (s.hasChildren()) continue;
+		c->add(s.name(), s.value().toString());
+	}
 }