New feature: drag-select in results grid, plus some minor fixes when opening images/folders

[inger147]

• New feature: You can now use the mouse to drag-select multiple adjacent result rows in the main grid. This can also be used along with the [Ctrl] key to select additional rows that are not adjacent to the rows being drag-selected.
• Added UseShellExecute to the process that opens an image file, so it will still work when a 32-bit application is set as the default to open images.
• Added a small delay (100 ms) after opening both a folder & image file, which facilitates the opening process, and when opening both folders or images at once, reduces the likelihood that the folders/images will open behind the AntiDupl application.
• Made some changes needed to compile the Release version in Visual Studio 2019.