Improve usability and style in web export presentation

- Check for WebGL support, don't load if unsupported
 - Check for IndexedDB support
 - Make canvas support check message visible
 - Colored debug output for warnings and errors
 - Make it obvious status can be closed by clicking
 - Don't use status to display non-critical errors
 - Limit output message count
 - Add clear output button
 - Fix setting total memory

platform/javascript/os_javascript.cpp

@@ -502,18 +502,12 @@ bool OS_JavaScript::main_loop_iterate() {
 
 		time_to_save_sync-=elapsed;
 
-		print_line("elapsed "+itos(elapsed)+" tts "+itos(time_to_save_sync));
-
 		if (time_to_save_sync<0) {
 			//time to sync, for real
-			// run 'success'
-			print_line("DOING SYNCH!");
 			EM_ASM(
-			  FS.syncfs(function (err) {
-			    assert(!err);
-				console.log("Synched!");
-			    //ccall('success', 'v');
-			  });
+				FS.syncfs(function(err) {
+					if (err) { Module.printErr('Failed to save IDB file system: ' + err.message); }
+				});
 			);
 		}