Issue #35: Implemented function TerminalInfoDouble in MtApi MT4

MtApi/EnumTerminalInfoDouble.cs

@@ -0,0 +1,8 @@
+namespace MtApi
+{
+    // https://docs.mql4.com/constants/environment_state/terminalstatus#enum_terminal_info_double
+    public enum EnumTerminalInfoDouble
+    {
+        TERMINAL_COMMUNITY_BALANCE  = 25 // Balance in MQL5.community
+    }
+}