Make gArgs aware of the arguments

gArgs knows what the available arguments are and their help. Getting
the help message is moved to gArgs and HelpMessage() is removed

src/init.h

@@ -8,6 +8,7 @@
 
 #include <memory>
 #include <string>
+#include <util.h>
 
 class CScheduler;
 class CWallet;
@@ -60,14 +61,11 @@ bool AppInitLockDataDirectory();
  */
 bool AppInitMain();
 
-/** The help message mode determines what help message to show */
-enum class HelpMessageMode {
-    BITCOIND,
-    BITCOIN_QT
-};
+/**
+ * Setup the arguments for gArgs
+ */
+void SetupServerArgs();
 
-/** Help for options shared between UI and daemon (for -help) */
-std::string HelpMessage(HelpMessageMode mode);
 /** Returns licensing information (for -version) */
 std::string LicenseInfo();