Resolved an issue finding the python interpreter on *nix systems, and

Windows 2008 R2 (32 bit), while running the pgAdmin 4 as runtime for
the PostgreSQL one click installers.

- Found a typo in runtime code, we were appending the path using ';' on
  *nix systems too. We should have used ':', and that did not allow the
  os.environ['PATH'] to identify the correct path of the python
  interpreter under the 'venv' directory.

- On Windows 2008, it was not honouring the environment variables, set
  under the Qt application (e.g. pgAdmin4.exe runtime), in the python
  application. (e.g. pgAdmin4.py). We will need to assume that - the
  python interpreter resides under the 'venv' directory outside the
  'bin' directory.

- Also, on windows 2008, it was setting PYTHONHOME environment variable
  to the full path of the pgAdmin4.exe, we need to reset it to 'venv'
  directory, if we find the python interpreter under it.

Thanks Murtuza Zabuawala for tips, and help.

runtime/Server.cpp

@@ -28,15 +28,25 @@ static void add_to_path(QString &python_path, QString path, bool prepend=false)
     {
         if (!prepend)
         {
+#if defined(Q_OS_WIN)
             if (!python_path.isEmpty() && !python_path.endsWith(";"))
                 python_path.append(";");
+#else
+            if (!python_path.isEmpty() && !python_path.endsWith(":"))
+                python_path.append(":");
+#endif
 
             python_path.append(path);
         }
         else
         {
+#if defined(Q_OS_WIN)
             if (!python_path.isEmpty() && !python_path.startsWith(";"))
                 python_path.prepend(";");
+#else
+            if (!python_path.isEmpty() && !python_path.startsWith(":"))
+                python_path.prepend(":");
+#endif
 
             python_path.prepend(path);
         }