Fixes to translatable strings

Sending an empty string to the translation system will not
result in getting an empty string back, but rather a description
of the currently loaded translations file. So empty strings
should not be marked as translatable.

Also adding some i18n comments and rewording a string I thought
was hard to understand.

Source/Core/Core/HW/GCPadEmu.cpp

@@ -97,10 +97,10 @@ GCPad::GCPad(const unsigned int index) : m_index(index)
       &m_always_connected_setting,
       // i18n: Treat a controller as always being connected regardless of what
       // devices the user actually has plugged in
-      {_trans("Always Connected"), _trans(""),
-       _trans("Always connected if checked.\n"
-              "If unchecked, it will link the emulated controller connection state\n"
-              "to the real default device connection state (if there is one).")},
+      {_trans("Always Connected"), "",
+       _trans("If checked, the emulated controller is always connected.\n"
+              "If unchecked, the connection state of the emulated controller is linked\n"
+              "to the connection state of the real default device (if there is one).")},
       false);
 }