Refactoring Project and Add .gitignore

[jinweijie]

I made several changes to the original project:

1. Change main form from "Form1" to "Main".
2. Add checked to files to be added to the list, for example, if a file named "hello.sqlgen", it will be added to the list which is not expected.
3. Add an icon to the application.
4. Remove signing.
5. Add .gitignore and removed unnecessary tracked files like bin, obj, .vs folder.

Thanks!