Improve the UX for the user when uploading new functions

[fioreb]

I think there are small changes that can improve the UX for the user:

The scroll functionality to change from one function to another should be only available when the user has the cursor on top of the pagination section, not on the whole page.
The pagination should be centered horizontally relative to screen height.
The submit button should be always visible in the bottom right corner.
Height of the web app fixed (remove scroll), we should only have scroll if the content doesn't fit in the screen height.

[PJColombo]

We should also remove the auto focus on mobile devices as well as fix the pagination component