Background mode (#32)

* Updated platform toolset version to v141_xp.
* Added comments related to old platform toolset. Need to delete them after testing on XP.
* Added gmock, updated gtest libs.

* Implemented and wrote a test for background mode functionality.
* Implemented of #27 (Open by default in the taskbar notification area);
* Added "Type here to search files" watermark to the main search field.

* Fixed bug with viewport incorrect size set for zero records;
* Other minor fixes (renaming, removing commented out code for debugging, etc.)

* Fixed hanging of the installer due to task rewrite dialog;
* Added removal from the registry for older versions during installation;
* Updated EULA and LICENSE files.
* Updated installerPickingUpScript to use the new signature procedure.

.gitignore

@@ -37,7 +37,7 @@ Release
 */bin/x86/Release/*
 
 /packages/Hardcodet.NotifyIcon.Wpf.1.0.5
-/.vs/Indexer/*
+/.vs/*
 
 /Installer/IndexerLogo.ico
 /Installer/UserSettings.xml