Generalize usage of System environment variables for processes

src/Core/WinSWCore/ServiceDescriptor.cs

@@ -72,7 +72,11 @@ namespace winsw
             Environment.SetEnvironmentVariable("BASE", d.FullName);
             // ditto for ID
             Environment.SetEnvironmentVariable("SERVICE_ID", Id);
-            Environment.SetEnvironmentVariable("WINSW_EXECUTABLE", ExecutablePath);
+
+            // New name
+            Environment.SetEnvironmentVariable(WinSWSystem.ENVVAR_NAME_EXECUTABLE_PATH, ExecutablePath);
+            // Also inject system environment variables
+            Environment.SetEnvironmentVariable(WinSWSystem.ENVVAR_NAME_SERVICE_ID, Id);
         }
 
         /// <summary>

src/Core/WinSWCore/WinSWCore.csproj

@@ -66,6 +66,7 @@
     <Compile Include="Util\SigIntHelper.cs" />
     <Compile Include="Util\XmlHelper.cs" />
     <Compile Include="WinSWException.cs" />
+    <Compile Include="WinSWSystem.cs" />
     <Compile Include="Wmi.cs" />
     <Compile Include="WmiSchema.cs" />
   </ItemGroup>

src/Core/WinSWCore/WinSWSystem.cs

@@ -0,0 +1,29 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace winsw
+{
+    /// <summary>
+    /// Class, which contains generic information about WinSW runtime.
+    /// This information can be used by the service and extensions.
+    /// </summary>
+    public class WinSWSystem
+    {
+        /// <summary>
+        /// Prefix for all environment variables being injected for WinSW
+        /// </summary>
+        public static readonly string SYSTEM_EVNVVAR_PREFIX = "WINSW_";
+
+        /// <summary>
+        /// Variable, which points to the service ID.
+        /// It may be used to determine runaway processes.
+        /// </summary>
+        public static string ENVVAR_NAME_SERVICE_ID { get { return SYSTEM_EVNVVAR_PREFIX + "SERVICE_ID"; } }
+
+        /// <summary>
+        /// Variable, which specifies path to the executable being launched by WinSW.
+        /// </summary>
+        public static string ENVVAR_NAME_EXECUTABLE_PATH { get { return SYSTEM_EVNVVAR_PREFIX + "EXECUTABLE"; } }
+    }
+}