Resolves #343 GUI and Frame Refactor

Major rewrite of the GUI into a module and view form, also using a new Feed class. The frame and frameset data structures have also been rewritten to support memory pooling and response frames.

applications/gui2/src/modules/addsource.cpp

@@ -33,6 +33,10 @@ std::vector<std::string> AddCtrl::getHosts() {
 	return std::move(io->feed()->knownHosts());
 }
 
+std::vector<std::string> AddCtrl::getGroups() {
+	return {};
+}
+
 std::set<ftl::stream::SourceInfo> AddCtrl::getRecent() {
 	return std::move(io->feed()->recentSources());
 }