Fixed SourceControlGUI import statement, renamed menu option from Git Configurations to Source Control

[MichaelM1]

Moved the import statement for SourceControlGUI in editor.py from inside the EditorWindow class to the top of the file. With this change, I was also able to delete the duplicate SourceControlGUI code in editor.py in favor of the version located in git.py. I also renamed the menu option from Git Configurations to Source Control.

[kencasimiro]

Looks good! Thanks Michael for correcting the rename and fixing the import issue for git.py

[MichaelM1]

I also added a menu tab called "Select Repository" where the user can input the file path of their repository. This will initialize the folder as a git repository if it isn't a repository yet.