New users find Minetest's account system confusing.
This change moves username/password to a new dialog,
with login and register buttons added to the Join Game tab.
The old registration confirmation dialog is removed in
favour of the new dialog.
Fixes#8138
* Android: Add zoom, minimap, and toggle chat button
Zoom button is put above jump button.
Minimap and toggle chat button are put in settings bar.
* Jump button is rotated down button
* Move three buttons on the right screen higher
