Add position retention back to feature creation menus

Since version 2.3.0, the feature creation menus (eg. for topologies and polgyons) always open in a set position, meaning you have to move your mouse across the screen to interact with them every time (strains the wrists!). However, in version 2.2.0, which I still use because of this issue, the menu appears wherever it was last time it was open. So for example, you could move the menu to have the next button overlap with the create feature button. Then each time you make a feature with marginally different properties, you can just click through without much effort. This is impossible in the newer versions, as far as I know, and it would be awesome to see return in a future version!