Import multiple files at once [INS-4633] [INS-4782]

[yaoweiprc]

Users can now import multiple files at once. There are two ways to do so:

1. Select multiple files by click the choose file link.
2. Select multiple files or folders in the file explorer and then use drag and drop, all selected files and subfiles within the directories will be parsed.

Other points to note:

1. Add restrictions to file formats that users can select.
2. Add a table view to show all resources or parse errors in each file.
3. Add loading status to scan button.
4. Will create a new workspace for each file user selected when user import multiple files to a project.