Make gui class contain all its control elements

[ceanwang]

These changes make the gui easy to be started by 3rd party code.

1. Moved the control elements initialization code from the bottom of the code into the init function
2. Changed all gui. into self. accordingly, like gui.Window.thread_mpi to self.Window.thread_mpi
3. Changed all variables as self. variable, like nt_entry to self.nt_entry

[OlivierWienholtz]

Hello Ceanwang
Thank for your contributions.

Can you please rebase the commits into 1 ?
This simplifies the commits...

Thanks !

[ceanwang]

Sorry, I am not familiar with github. Don't know what am doing. I am using Windows 10.
What should I do? Maybe re-create a clean pull request?

[OlivierWienholtz]

Dear CeanWang
Indeed we can help you to get into the Workflow.
I just saw that you use your main branch to perform the changes.
In git, main branch remains clean & changes are done in development branches.

Here are some pages about Workflow & Git:
Our How to contribute :
https://github.com/OpenRadioss/Tools/blob/main/Contributing.md
At GitHub Some documentations :
https://docs.github.com/en/get-started/using-github/github-flow

you can also contact communitymanager@openradioss.org
We can help you on this.

Best Regards,
Olivier