This patch cleans up "simple mode". I rearranged some buttons and hide the leftmost column in this mode. X³ as a function is now in the column, where x², x^y and so on can be found. I think, it is now easier to find the functions. The rightmost colum with memory functions is hidden in this mode too.
Furthermore, I rearranged the order of highlighted buttons by pressing the tab-button. This patch is highly inspired by the mockup of the reporter of bug https://bugs.kde.org/show_bug.cgi?id=254369 .
I hope you enjoy
* Tested the tab order
* tested hide/show of modes