Overload [] operators for getting and setting selected inputs

[Aecrionx]

Hello LovetheFrogs, you have a cool project so I thought I could add some extra features like overloading the [] operator so there's no need to type the whole .get_input() / .set_input() methods. I have also added a section to the remove_input() method so it is possible to delete an input given an index number.

I have also changed the testing files for logic gates to be different asserts statements because I thought it would be easier to go to the line where the error is directly. Instead of finding the string that belongs to an if-statement now it's possible to go directly to the line causing the problem.

If you like/agree with these changes feel free to accept the pull request.

[LovetheFrogs]

Hi! I appreciate your PR, as I'm fairly new with OO Python and I did not think about getitem and setItem. However, I did the tests that way as they were easier for me to read and execute, tho I assume it depends on each own personal liking. I'll wait for your opinion on that for the merge of the branch. Thanks for your contribution!

[Aecrionx]

I separated the tests into different assert statements because when the interpreter catches the error it tells you exactly which case (or line) is causing the problem. When you have a project that has hundreds of tests this might save you some time, I think.

[LovetheFrogs]

okay it seems reasonable when doing a bunch of tests of some module. I will be doing that for sure for some modules i have in mind. I'm accepting your PR, thanks for all!