NOISSUE simplify system detection and user agent handling

Now it only checks OS kernel name/version.
User agent is 'MultiMC5/$version'.
Kernel info is passed through custom dimensions in analytics.

libraries/ganalytics/include/sys.h

@@ -3,11 +3,13 @@
 
 namespace Sys
 {
-/**
- * Get operation system name and version.
- * @return os       A QString with the name and version of the operating system.
- */
-QString getSystemInfo();
+struct KernelInfo
+{
+	QString kernelName;
+	QString kernelVersion;
+};
+
+KernelInfo getKernelInfo();
 
 uint64_t getSystemRam();